Hybrid all digital fiber to CATV cable system and method

ABSTRACT

Producing advanced HFC CATV cable systems while easing the burden of backward compatibility. The system improves CATV data carrying capacity by moving RF QAM modulators from the cable head end to various individually or group addressed optical fiber nodes supplying neighborhood CATV cables, and sending data from the cable head IP backbone to the nodes over optical fiber as IP data packets. For high backward compatibility, the system digitizes legacy RF waveforms, or demodulates legacy QAM waveforms to QAM symbols, also transmits these over the optical fiber as IP data packets, and then reconstitutes back to original waveforms as needed. The system is thus able to easily handle legacy NTSC, FM, QPSK waveforms and do partial (QAM symbol level) compression of legacy QAM waveforms to and from multiple nodes without requiring additional optical fiber wavelengths. The system may use non-standard upstream/downstream CATV frequency splits, filter bank receivers, and FPGA/DSP/ASIC methods.

CLAIM OF BENEFIT TO PRIOR APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/328,494, filed Jul. 10, 2014; U.S. patent application Ser. No.14/328,494 is a continuation of U.S. patent application Ser. No.13/674,936, filed Nov. 12, 2012, now issued as U.S. Pat. No. 8,782,729;U.S. patent application Ser. No. 13/674,936 is a continuation in part ofU.S. patent application Ser. No. 13/555,170, filed Jul. 22, 2012, nowissued as U.S. Pat. No. 8,644,706; U.S. patent application Ser. No.13/555,170 in turn claims the benefit of provisional application61/511,395, filed Jul. 25, 2011; U.S. patent application Ser. No.13/674,936 is also a continuation in part of U.S. patent applicationSer. No. 12/907,970, filed Oct. 19, 2010, now issued as U.S. Pat. No.8,826,359; U.S. patent application Ser. No. 13/674,936 is also acontinuation in part of U.S. patent application Ser. No. 13/346,709,filed Jan. 9, 2012, now issued as U.S. Pat. No. 8,510,786; U.S. patentapplication Ser. No. 13/674,936 is also a continuation in part of U.S.patent application Ser. No. 13/035,993, filed Feb. 27, 2011 now issuedas U.S. Pat. No. 8,365,237; U.S. patent application Ser. No. 13/674,936is also a continuation in part of U.S. patent application Ser. No.12/692,582, filed Jan. 1, 2010, now issued as U.S. Pat. No. 8,311,412;U.S. patent application Ser. No. 13/674,936 is also a continuation inpart of U.S. patent application Ser. No. 13/400,415, filed Feb. 20,2012, now issued as U.S. Pat. No. 8,863,213; U.S. patent applicationSer. No. 13/674,936 is also a continuation in part of U.S. patentapplication Ser. No. 13/478,461, filed May 23, 2012, now issued as U.S.Pat. No. 8,773,965; U.S. patent application Ser. No. 12/907,970 claimsthe priority benefit of U.S. provisional application 61/385,125, filedSep. 21, 2010; U.S. patent application Ser. No. 13/478,461 claims thepriority benefit of U.S. provisional application 61/622,132, filed Apr.10, 2012; all have the inventor Shlomo Selim Rakib; the contents of allof these applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Cable television (CATV), originally introduced in the late 1940's as away to transmit television signals by coaxial cables to houses in areasof poor reception, has over the years been modified and extended toenable the cable medium to transport a growing number of different typesof digital data, including both digital television and broadbandInternet data.

Over the years, this 1940's and 1950's era system has been extended toprovide more and more functionality. In recent years, the CATV systemhas been extended by the use of optical fibers to handle much of theload of transmitting data from the many different CATV cables handlinglocal neighborhoods, and the cable head or operator of the system. Herethe data will often be transmitted for long distances using opticalfiber, and the optical (usually infrared light) signals then transformedto the radiofrequency (RF) signals used to communicate over CATV cable(usually in the 5 MHz to 1-GHz frequencies) by many local optical fibernodes. Such systems are often referred to as hybrid fiber cable systems,or HFC systems. The complex electronics that are used by the cableoperator to inject signals (e.g. data) into the system, as well asextract signals (e.g. data) from the system are often referred to asCable Modem Termination Systems or CMTS systems.

A more detailed discussion of prior art in this field can be found incopending application Ser. No. 12/692,582, the contents of which areincorporated herein by reference.

Prior art work with various types of CMTS systems and fiber nodesincludes Liva et. al., U.S. Pat. No. 7,149,223; Sucharczuk et. al. USpatent application 2007/0189770; Sawyer et. al., US patent application2003/0066087; and Amit, U.S. Pat. No. 7,197,045.

BRIEF SUMMARY OF THE INVENTION

As user demand for ever increasing amounts of downstream and upstreambandwidth increases, further improvement and advances in HFC technologyare needed.

The invention is based, in part, upon the realization that in order tomake further advances in HFC technology, deviations from both the priorart schemes to allocate upstream and downstream data on the CATV portionof the HFC network, and deviations from the prior art schemes toallocate upstream and downstream data on the fiber portion of the HFCsystem, would be useful.

In order to make massive improvements in system performance, in someembodiments it will be useful to implement new schemes for datatransmission on the optical fiber portion of the HFC network, andimplement new schemes for data transmission on the CATV portion of theHFC network as well.

The optical waveforms presently used on the fiber portion of opticalfiber wavelengths of present HFC systems are often just frequencyshifted versions of the same waveforms used to transmit RF signals onthe CATV cable. Although these direct RF to optical and back to RFwaveform reproduction methods have the advantage of simplicity, due tovarious optical fiber signal propagation effects, such as Ramanscattering, such RF to optical shifted CATV waveforms make inefficientuse of available optical fiber spectrum. This is because various opticalfiber effects, the various waveforms become smeared or distorted,resulting in crosstalk between neighboring optical fiber wavelengths,and the CATV waveforms are not at all optimized to cope with theseeffects. By shifting to alternative types of waveforms, such as thewaveforms used to transmit Gigabyte Ethernet (GigE) signals (which oftenuse more distortion resistant waveforms such as binary phase shift keyed(BPSK) or quadraphase-shift keying (QPSK) modulation), a much higheramount of data may be sent over the optical fiber. The rate of datatransmission per wavelength can be much higher, and differentwavelengths may be spaced much closer together.

At the same time, on the radio-frequency (RF) side of the HFC network,the CATV spectrum is also used inefficiently. Much of the available 5MHz to approximately 1 GHz CATV frequency is presently filled up withQAM channels that, most of the time, are carrying downstream data thatis not actually being used (at that time) by the various households thatare connected to the cable. Another problem is that only a tiny regionof CATV spectrum (usually 5-42 MHz), is allocated for upstream data.This relatively narrow region of frequencies must carry the upstreamdata for the entire CATV neighborhood. This results in great limitationson the bandwidth or amount of data that can be uploaded from the varioushouseholds. Thus typical CATV systems are asymmetric, with thedownstream data rates being much higher than the upstream data rates.

The invention teaches new HFC systems and methods to carry much higheramounts of upstream and downstream data. On the fiber portion of the HFCsystem, the invention teaches use of non-CATV compatible waveforms (e.g.GigE rather than QAM waveforms) which can carry much higher amounts ofdata over long distances. On the cable portion of the HFC system, theinvention teaches improved systems and methods that utilize the limited5 MHz to 1-GHz bandwidth of CATV cable more efficiently.

The invention operates, in part, by use of intelligent optical fibernodes, and is in part a further extension of the CMRTS optical fibernodes previously discussed by copending U.S. patent application Ser. No.12/692,582 and the other copending patent applications previouslydiscussed.

In some embodiments, the invention may be a system or a method based ondigital optical fiber nodes operating in a Hybrid-Fiber CATV-Cable (HFC)network. Such systems generally comprise a cable head end, which isoften in IP communication with an IP backbone such as the Internet orother high speed digital network. These HFC networks also generally alsocomprise one or more optical fibers in communication with the head end,as well as at least one and often many digital optical fiber nodes(DOFN).

These digital optical fiber nodes have some elements in common with theCable Modem Remote Termination Systems (CMRTS) and Digital Cable ModemRemote Termination systems (D-CMRTS) previously described in variouscopending applications such as parent U.S. application Ser. Nos.12/692,582, 61/385,125, 12/907,970, 13/346,709, 13/478,461, and13/555,170, the contents of which are incorporated herein by reference.As a result, these digital optical fiber nodes (DOFN) will frequently bediscussed in the alternative in this disclosure as D-CMRTS units.

To form an HFC system, these various DOFN or D-CMRTS units will beconnected to (i.e. in RF communication with) various CATV cables (e.g.coax cable, capable of RF transmissions), and at least one CATV cabledevice which will be various cable modems, set top boxes, digitaltelevisions, computers, and the like.

Although, as discussed in the earlier disclosures as well, theinventor's earlier D-CMRTS units were designed from the beginning with ahigh capability to provide additional data handing capability to CATVsystems (e.g. above and beyond the present DOCSIS 3.0 standard), onechallenging problem is how to provide even more functionality whilestill providing the ability to gracefully operate in an environment withlarge amounts of legacy equipment.

A unique aspect of the present disclosure is that the improved DOFN orD-CMRTS units disclosed herein, while providing advanced functionality,and often totally abandoning use of optical versions of the standardQAM, NTSC, FM waveforms on optical fiber, are still highly capable ofoperating with legacy equipment.

Here, systems are disclosed that are designed with a high capability tooperate in the digital optical fiber domain (e.g. using optical fiberdigital transport protocols such as GigE) while still providing CATV RFsignals carrying various types of legacy analog CATV RF waveforms, suchas analog NTSC television channels, FM audio channels, QPSK channels,QAM channels and the like. The present methods have the additionaladvantage that because digital data transport protocols can easily carrydata packets to and from many alternative addresses, the invention'smethods can operate without requiring the use of, for example, largenumbers of alternative optical fiber wavelengths. By contrast, underprior art methods, use of large numbers of alternative optical fiberwavelengths was required in order to accommodate the many differenttypes of analog legacy CATV waveforms that can originate from manydifferent types of legacy optical fiber nodes.

According to the invention, such improvements can be made by, forexample, converting legacy CATV analog waveforms to a digital form byhigh speed analog to digital converters and or QAM waveform demodulationinto the underlying QAM symbols. This approach has the advantage thatthese waveforms can then be transformed to digital data packets (IP datapackets) without the system otherwise needing to understand what theunderlying data content of the waveforms is.

(For further discussion on QAM symbol methods, please see copendingapplication Ser. No. 13/478,461 “EFFICIENT BANDWIDTH UTILIZATION METHODSFOR CATV DOCSIS CHANNELS AND OTHER APPLICATIONS”, the contents of whichare incorporated herein by reference.

The digitized waveform data can then be transported as IP packets overthe HFC optical fibers using digital optical fiber data transmissionformat such as GigE.

More specifically, CATV legacy downstream RF waveforms of any type (e.g.NTSC, FM, QPSK) and/or more standard CATV downstream RF waveforms suchas various QAM waveforms can be digitized by using a high speed analogto digital converter or other method to sample and digitize these legacydownstream RF waveforms, thus producing digital samples of the legacydownstream RF waveforms. This digital data which can then be convertedto IP packets and sent over the optical fiber. Alternatively, and moreefficiently in the case where more standard RF QAM waveforms are beingtransmitted downstream, these RF QAM waveforms, which are complexwaveforms constructed using various underlying QAM symbols, may bedemodulated and the underlying QAM symbols determined. These demodulatedQAM symbols can then also be converted to various data packets andoptically transmitted downstream over the HFC optical fiber or fibers.

Once in the form of IP data packets, low cost equipment such asinexpensive switches can then be used to easily sort and transport theseIP data packets to and from various devices.

To reconstruct these various legacy CATV RF waveforms, at the digitaloptical fiber node(s) or D-CMRTS unit(s), various RF digitalreconstitution devices may be configured to accept the digital samplesof downstream RF waveforms (which were digitally transmitted downstreamover the optical fiber), and reconstitute these digital waveform samplesinto one or more downstream digitally reconstituted RF waveformschannels that essentially reproduce the original RF waveforms.

Alternatively or additionally, at the digital optical fiber node(s) orD-CMRTS unit(s) there can also be one or more remodulator devicesconfigured to accept the downstream digital QAM symbols that weretransmitted over the optical fiber, and remodulate these QAM symbolsinto one or more downstream QAM symbol, again producing remodulated RFQAM waveforms and channels that essentially reproduce the original RFQAM channels.

To provide still higher levels of service (e.g. to provide higher CATVdata carrying capability, and provide functionality beyond the presentDOCSIS 3.0 standard), the digital optical fiber nodes or D-CMRTS unitswill often also contain one or more IP to QAM conversion devices such asQAM modulators. These QAM modulators may be configured to acceptdownstream digital IP data packets transmitted over the optical fiber,and to modulate these digital IP data packets into one or moredownstream IP based RF QAM channels. These can be broadcast QAMchannels, narrowcast QAM channels, on-demand QAM channels, and so on.

Often, according to the invention, the digital optical fiber nodes orD-CMRTS units will employ two or more of the above options, and willthus use a RF combiner device configured to combine any of thesedigitally reconstituted RF channels, QAM symbol remodulated RF QAMchannels and these IP based RF QAM channels, and then transmit thesevarious RF channels downstream over the CATV cable to the various CATVcable devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overall view of the various frequencies and datachannels that are presently allocated for a typical CATV cable carryinglegacy analog television FDM channels, QAM digital television channels,and various types of DOCSIS data.

FIG. 2 shows an overall view of the various wavelengths allocated forprior art optical fiber wavelength division multiplexing schemes (150)and dense wavelength division multiplexing (DWDM) schemes (160).Although the present invention may use DWDM methods, it does not requirethem, and to some extent reduces the need for DWDM methods because itcan fit more types of digital data onto a single wavelength using, forexample, GigE optical data packets (170).

FIG. 3 shows a simplified version of how prior art HFC systems transmitdata from the cable head to different optical fiber nodes servingdifferent neighborhoods

FIG. 4 contrasts the difference in downstream data transmission betweena prior art HFC system that operates using a 1310 nm optical fiberinfrared signal analog according to typical CATV waveforms (e.g. manyQAM waveforms), and the invention's improved digital transmissionmethods. In contrast to prior art, because the invention can transmitsall CATV data in digital form using various data packets, the highereffective data rate and superior addressing capability of IP datapackets allows more different types of data to be sent on the samewavelength. The invention preserves backward compatibility by providingvarious converters to convert back and forth between legacy waveformsand IP data packets.

FIG. 5 shows an overview of the invention in operation in downstreammode, showing how the improved “smart” D-CMRTS fiber nodes can transporta higher effective amount of customized data downstream for users.

FIG. 6 shows how the invention may also reparation the CATVupstream/downstream frequency split from the standard (US) 5-42 MHzupstream frequency range, into an alternate and often broader upstreamfrequency range. This helps the system transmit a far greater amount ofupstream data from local neighborhoods to the cable head.

FIG. 7 shows a more detailed view showing one embodiment of how theD-CMRTS fiber nodes may operate.

FIG. 8 shows additional details of how the CMRTS portion of the D-CMRTSfiber node may operate. The CMRTS portion provides much of the higherfunctionality of the system.

FIG. 9 shows more details of how the virtual shelf manager and theconfiguration database may control the functionality of most or all ofthe various D-CMRTS fiber nodes, and optionally other active nodes andswitches in the HFC network system.

FIG. 10 shows a residential gateway (1100) that can also convert betweena CATV cable system with an extended frequency allocated for upstreamdata (e.g. 5-547 MHz or alternative upstream range of frequencies), andresidential equipment designed for the standard 5-42 MHz range ofupstream frequencies.

DETAILED DESCRIPTION OF THE INVENTION

Nomenclature: In this specification, the term “legacy signals” willoften be used to describe various older standard CATV RF signals such asNTSC (television) signals, FM radio signals, set top box signals and thelike. It should be understood, however, that the invention's methodswill in fact operate with any type of RF signal. Thus the term legacysignals, although intended to improve readability by reminding thereader that the invention's methods are particularly useful for copingwith various CATV legacy RF waveforms, is not otherwise intended to belimiting.

As previously discussed, prior art schemes of transmitting HFC data inthe form of one or more CATV analog modulated wavelengths of light,along optical fiber, tended to be inefficient. That is, the prior artmethods limited the amount of data that could be sent. This is becausethe analog waveforms used to transmit RF signals on CATV cable workinefficiently when transposed to optical wavelengths. Due to variouseffects including Raman scattering, and other nonlinear optical fibereffects, when too many analog modulated light wavelengths are placedonto an optical fiber too close together (in terms of wavelengthdifferences), cross-talk between the different wavelengths tends todegrade the complex CATV RF analog signals (usually composed of many QAMmodulated waveforms) to the point where crosstalk may render the signalsuseless.

As a result, to prevent the CATV modulated analog signal fromdegradation when carried over optical fiber, the wavelengths must berather widely spread out. Thus due to cross talk effects, an opticalfiber may only be capable of transmitting a few (e.g. 8) inefficientlymodulated CATV signals, each transmitting about 6 Gigabits of data persecond.

By contrast, if more efficiently digitally modulated signals (e.g. GigEdata formats) were used, the same stretch of optical fiber might becapable of transmitting many more wavelengths (e.g. 80) of signals, andeach wavelength in turn may transmit far more data, such as between10-100 Gigabits of data per second.

Copending application Ser. No. 12/692,582 taught the advantages ofproducing a new type of optical fiber node, there called a Cable ModemRemote Termination System (CMRTS) device, which essentially pushed muchof the functionality (such as generating QAM signals) of the prior artCable Modem Termination Systems (CMTS) from the central cable head downto many distributed optical fiber nodes servicing neighborhood CATVcables. Thus according to application Ser. No. 12/692,582, non-CATVcompliant signals may be sent to and from the central cable head tovarious remote CMRTS optical fiber nodes by optical fibers carryinglight modulated by more efficient digital Ethernet protocols (e.g. GigEsignals). The CMRTS optical fiber nodes then converts these non-CATVcompliant signals into CATV compliant RF signals, such as a plurality ofdifferent RF QAM modulated signals, and/or other types of signals.

The present invention further builds upon this concept, and furtherteaches the advantages that can be obtained by reducing or droppingadditional backward compatibility requirements, such as the requirementthat legacy RF waveforms (e.g. QAM waveforms) be transmitted along theHFC optical fiber(s) while preserving the essential waveformcharacteristics (e.g. requiring that the optical QAM waveforms be thesame as the RF QAM waveforms).

Other departures from pure backward compatibility may also be reduced.For example, according to the invention, the prior art CATV upstreamrequirements that upstream data must be carried as a number of 2 MHzwide QAM channels in the 5-42 MHz region, may be dropped in favor ofalternate upstream schemes that provide for greater amounts of upstreamdata to be transmitted. That is the 5-42 MHz region may be extended intothe higher frequency ranges—for example extended to the 5-547 MHzregion, which will allow for a higher rate of upstream data to betransmitted, but of course will cut into the rate of transmission ofdownstream data.

However even if the upstream bandwidth problem is solved at the CATVcable side of the HFC system, the optical fiber itself, if usedaccording to prior art schemes (e.g. shove the analog signal over theoptical fiber in an essentially unchanged form) will now be ratelimiting. That is, if a large number of different neighborhoods, eachwith their own stretch of CATV cable, are now enabled to starttransmitting much more upstream data, unless the method of sending dataover the fiber portion of the HFC network is changed, there will soon bea bottleneck at the fiber stage. This is because the prior art HFCmethods of handing upstream data would, in general, simply convert theanalog RF modulated CATV upstream waveforms into equivalently modulatedoptical fiber infrared light waveforms, and then transmit this data backover the optical fiber. Although such conversion processes can be easilydone with inexpensive converters, this scheme has the drawback, aspreviously discussed, that they are not optimized for optical fiber.Consider the problem of pooling upstream data from multipleneighborhoods. Although the data CATV RF data from each neighborhoodmight be converted to a slightly different infrared frequency, put onoptical fibers, the fibers combined and a composite multiple wavelengthsignals sent upstream, the inefficient CATV RF modulation schemes meanthat each wavelength will carry only a relatively small amount of data.Further, due to crosstalk effects, the number of different neighborhoodsworth of data that can be pooled is also limited. So due to prior-artinefficiencies, the potentially very large ability of the optical fiberto carry upstream data rapidly becomes limiting.

However, again by reducing the requirements that the HFC system be fullybackward compatible in terms of inefficiently carrying legacy analog RFwaveforms over optical fiber; the much higher amount of upstreambandwidth that would be generated under the invention can now be handledby repackaging the upstream data into more efficient modulation formats,such as the digital (GigE) modulation format, before transmitting thedata on the optical fiber. Thus, according to the present invention, asmaller number of higher data density and more efficiently modulatedoptical fiber optimized signals, such as GigE data packets may now sent.This overcomes the inefficiencies of prior-art optical fiber modulationschemes, and helps remove the optical fiber upstream transmissionbottleneck.

As per copending application Ser. No. 12/692,582, the present disclosurerelies, in part, upon a radically different CMTS design in which the QAMmodulators in the CMTS PHY section (used to ultimately provide thewaveforms used to send RF data signals to a given individual cable) areoften not located at the central cable head, but rather are divided andpushed out to the distant optical fiber nodes of the HFC network. Thatis, in contrast to prior art designs, were the QAM modulators were arelocated in the PHY units of main (centralized, e.g.—cable head) CMTSline cards on the central CMTS units; in the present invention, some orall of the QAM modulators are located in the PHY sections of remote ordistributed CMRTS optical fiber nodes.

Alternatively, where for greater compatibility with legacy equipment isdesired, at least some of the QAM modulators, or other RF signalgenerators such as NTSC television, FM radio, set top box QPSK signalsand the like can still remain at the head end. However in thisembodiment, the legacy RF waveforms output by the legacy head endequipment will usually be digitized before optical transmission. Thisdigitization can be done by various means, including high frequencyanalog to digital sampling, or by for example demodulating various QAMwaveforms, determining the underlying QAM symbols used to generate theQAM waveforms, and digitally sending the results. At the optical fibernode, these RF waveforms can then be regenerated, for example by digitalto analog conversion and RF modulation, or using the digitally sent QAMsymbols to control one or more RF QAM modulators.

Often however, it will be useful to simply send the data to the variousoptical fiber nodes in the form of standard IP packet type digital data.The optical fiber nodes can examine the data packets, determine whichpackets correspond to what signals, and for example then use theappropriate data packets to drive various optical fiber located RF QAMmodulators (e.g. for broadcast QAM signals, narrowcast QAM signals,DOCSIS QAM signals, etc.) as desired.

In the prior Ser. No. 12/692,582 application, these advanced opticalfiber nodes with local QAM modulators were called Cable Modem RemoteTermination System (CMRTS) units. Here, to better emphasize the abilityof the present invention to function using Digital Wavelength DivisionMultiplexing (e.g. use of alternate data transmission formats such as1GigE, 10GigE, EPON, BPON, GPON, 10GPON, SONET, Fiber Channel, FSAN, andthe like) here the still more capable CMRTS units of the presentinvention will be termed D-CMRTS units, where the D may be used tosymbolize the Digital encoding/decoding methods of the D-CMRTS unitswith respect to legacy signals

To better emphasize the changes in functionality at the head end of theHFC system, the higher capacity cable modem termination system (CMTS) atthe head end will often be referred to as D-CMTS units, where the Dagain is used to symbolize the digital encoding capability of the D-CMTSunits.

As per the CMRTS units that were previously disclosed in Ser. No.12/692,582, the D-CMRTS units disclosed herein will often also belocated at the final network fiber nodes (FN) between the fiber portionsof the HFC system, and the cable portions of the HFC system.

In the CMTS systems discussed in Ser. No. 12/692,582, some QAMmodulators were located in the centralized CMTS PHY sections at thecable head, while some QAM modulators were located at the remote CMRTSunits. The CMTS QAM modulators were used for sending data, such as astandardized package of cable TV channels and perhaps a basic level ofDOCSIS service, which might be generally requested by manyneighborhoods; over optical fiber using RF CATV (e.g. QAM) modulatedinfrared light signals. This helped maintain backward compatibility withprior art HFC systems.

Although in this present disclosure, in order to focus on aspects of theinvention that can provide higher amounts of upstream and downstreamdata to subscribers, this type of backward compatibility is notdiscussed in as much detail. However in some embodiments, the methods ofthe present disclosure may also take advantage of these backwardcompatible aspects of Ser. No. 12/692,582. For example, some QAMmodulators may continue to send CATV modulated (e.g. QAM) waveforms overoptical fibers at certain legacy wavelengths, such as 1310 nm, asdesired, and these can be converted back to QAM RF signals at theoptical fiber node by simple optical to electronic (O/E) transducers.

In other words, the present all digital invention does not becomeinvalid simply because someone puts standard CATV waveforms on theoptical fiber (for example at a different wavelength than thewavelengths used by the invention). It is possible to contemplate, forexample, a mixed neighborhood system where the invention's all digitalmethods are used for some neighborhoods being supplied by an opticalfiber at a first set of optical wavelengths, and legacy equipmentfunctions in other neighborhoods being supplied by the same opticalfiber, but operating at a second set of optical fiber wavelengths.

In a preferred embodiment, to maintain backward compatibility, thevarious legacy head end waveforms, such as QAM waveforms, NTSCtelevision waveforms, QPSK waveforms and the like (during transmissionover optical fiber both downstream from the head end to the opticalfiber nodes, and upstream from the optical fiber nodes to the head end)can be digitized for transmission by various methods, and thenreconstituted after optical fiber transmission. As previously discussed,these digitization methods can range from brute force (i.e. simple highspeed analog to digital sampling at around the Nyquist frequency (e.g.2× the highest frequency of the underlying waveform), as well as moresophisticated methods such as demodulating the various QAM waveforms toextract the underlying QAM symbols used to produce the waveform in thefirst place.

Often the brute force, high frequency analog to digital sampling methodsmay be more suitable for legacy NTSC, FM, or QPSK waveforms (channels).By contrast, QAM demodulation methods may be more suitable for QAMchannels transmitting various SD or HD digital television, DOCSIS QAMchannels, and the like.

In general, however, digitally sending IP data packets, such as IP datapackets containing a variety of data such as broadcast QAM channels,narrowcast QAM channels, DOCSIS channels, and other types of channelstends to be more efficient (i.e. minimizes the bits per second raterequired). Thus when not needed for legacy purposes, generally themethods described herein will tend to prefer use of methods thattransmit data to the optical fiber nodes using IP data packets (e.g.GigE format), and the optical fiber nodes in turn will take these IPdata packets and convert them to the various QAM waveforms and the likerequired for RF transmission over the CATV cable.

Thus some embodiments of the present invention may elect to have no QAMmodulators at the cable head whatsoever, and send pure non-CATVcompatible waveforms (e.g. digital IP data packets) through the opticalfibers. These systems may rely on the remote D-CMRTS units to generateall of the downstream QAM signals in the system.

Thus in one embodiment, the invention may be a method for enhancing thedata carrying capacity of a hybrid fiber cable (HFC) network with acable head, an optical fiber network, a plurality of optical fibernodes, a plurality of individual CATV cables connected to the pluralityof optical fiber nodes (D-CMRTS units), and a plurality of individualcable modems, each with differing data requirements, connected to eachof the individual CATV cables.

This method may work by using at least one optical fiber, operating atone or more wavelengths, to transport a first set of downstream datafrom the cable head to the optical fiber nodes. This first set ofdownstream data may be transmitted in a digital format that is notcapable of being directly injected into individual CATV cables by simpleoptical to RF converters.

Here, generally so much data may be transmitted that if all of the firstset of downstream data was converted into RF QAM waveforms, thebandwidth of this data would exceed the available bandwidth of any ofthe individual CATV cables in the system. To avoid this problem,generally only a selected portion of this first set of downstream datawill be converted into downstream RF QAM waveforms at these opticalfiber nodes.

What portions of the optical fiber downstream data are selected for anygiven CATV cable neighborhood (with its own optical fiber node and CATVcable) may differ. At the optical fiber nodes, data packets will beselected, and these selected data packets will be converted intodownstream RF QAM waveforms that in turn will be injected into theindividual CATV cables.

Here, the main constraint is that for each individual CATV cable thedownstream RF QAM waveforms should be selected so that the sum total ofthe selected downstream RF QAM waveforms do not exceed the availablebandwidth of the individual CATV cables.

In a preferred embodiment, the invention's D-CMRTS units will often bedesigned to be highly software configurable, so that the ability of theD-CMRTS units to operate their remote or distributed QAM modulators tosend downstream data, as well as the ability of the D-CMRTS units tooperate various RF packet processors that receive multiple RF bursts ofmodulated upstream data from various cable modems, demodulate thebursts, digitize and reassemble this upstream data into packets, andretransmit this data back upstream, can be reconfigured by remotesoftware. Such methods can greatly simplify the management andconfiguration of the distributed D-CMRTS network.

As one simplified example, in order to supply a standardized set of TVchannels and other services to three cables in three neighborhoods, thehead end equipment may have QAM modulators in their PHY units (See FIG.7, 614) set to drive an optical fiber with multiple QAM signals atoptical wavelengths.

If backward compatibility is desired, then head end may have digitalconverter units (399) that intercept output from the legacy head endQAM, FM, QPSK modulators and other RF modulators (614), and digitizethis output by relatively brute force methods (high speed analog todigital converters, QAM demodulation into QAM symbols). The digitaloutput from these converters can then be transmitted along optical fiber(218) along with other digital traffic (e.g. from GigE PHY modulators620) to the optical fiber nodes.

In some neighborhoods, simple “dumb” converters and “dumb” optical fibernodes can take this digital data from the legacy head end equipment(614), and convert it back to legacy QAM, FM and QPSK signals by varioussimple methods such as digital to analog conversion (600), QAMremodulation using the QAM symbols (603), and the like. These “dumb”converters and optical fiber nodes can then inject these reconstitutedRF signals into those neighborhood CATV cables (226) that are equippedwith “dumb” converters and optical fiber nodes.

If backward compatibility is not desired, in some embodiments, the cablehead end may have no QAM modulators (or other modulators such as FM andQPSK modulators in their CATV PHY units 614), and all signals going outto the various D-CMTRS optical fiber nodes along the fiber portion ofthe network (218) may be digitally modulated in GigE or other format.Please refer to Ser. No. 12/692,582 for a more detailed discussion ofthe backward compatibility options.

Some of the examples in this specification, such as FIG. 7, show a mixedmode of operation, where some legacy “dumb” converters and optical fibernodes in some neighborhoods work in conjunction with more advancedD-CMRTS optical fiber nodes in other neighborhoods. Other examples showa pure GigE mode where backward compatibility with dumb optical fibernodes is no longer required.

Since the D-CMRTS units will often use optical fibers and variousDigital Ethernet (GigE) protocols as their primary means ofcommunication, this GigE fiber data will require conversion,reformatting, and QAM modulation by the components (e.g. 600, 603) inthe remote D-CMRTS units (304). The QAM modulators in the D-CMRTS unitswill then provide a radiofrequency (RF) QAM signal that can be injectedinto the cable, and recognized by cable modems attached to the variouscables.

As previously discussed, one of the biggest advantages of generatingsome or all of the CATV RF data at the local D-CMRTS optical fiber nodeis that vast amounts of data can be carried by the optical fiber usingmodulation schemes, such as the various digital GigE data transmissionschemes, that may be optimized for the signal transmissioncharacteristics of the optical fiber media. That is, by eliminating theneed for direct and simple conversion to and from the signal waveforms(often QAM waveforms) used to send RF data on CATV cables, the opticalfiber signals can both carry more data per wavelength, and also allowfor a greater number of signals at nearby optical fiber wavelengths tobe sent with minimal interference.

As per the prior Ser. No. 12/692,582 disclosure, the present disclosurealso relies, in part, upon the observation that at the present level ofrather coarse granularity (where multiple neighborhoods are served bythe same CATV QAM signals) the aggregate demands for IP-on demand datafrom multiple cables serving multiple neighborhoods may easily saturatethe limited CATV bandwidth. That is, absent some sort of customization,it is not possible to send all data to everybody because it won't fit onthe CATV cable. However at a finer level of granularity (where eachneighborhood might get its own customized CATV signal), the IP-on demanddata for an individual neighborhood is more likely to fit within thelimited bandwidth of each neighborhood's CATV cable.

The trick is thus to avoid overloading each neighborhood's particularCATV cable bandwidth by picking and choosing the mix of standard QAM andQAM IP/on-demand signals are delivered to each neighborhood. As per theprior Ser. No. 12/692,582 disclosure, the present disclosure's scheme ofdelivering a potentially ever changing mix of neighborhood specific CATVchannels and data services creates some rather complex networkmanagement issues, however. Here the computer control systems previouslydiscussed for Ser. No. 12/692,582 may be used.

The computer control system may, for example, manage the availablebandwidth on the various cables that serve the various neighborhoods.When used in a backward compatible first option mode, the “standard” QAMchannels (if any) that are transmitted may be fixed by the cableoperator in advance, and these may remain relatively constant. When usedin the less backward compatible, higher performance mode, thecomputerized system may vary both the “standard” QAM channels (if any)being transmitted by any given central D-CMRT line card, as well as theuser-customized or “premium” IP/on-demand QAM channels being transmittedby the remote D-CMRTS units.

In CATV jargon, the various CMTS systems at the cable head are oftenreferred to as a “shelf” or “CMTS shelf” (500). Although the inventiondistributes the functionality of the CMTS unit from the cable head toD-CMRTS units that may be distributed to the far-flung optical fibernodes throughout the entire network, from a network managementperspective, in some embodiments, it may be simpler for the othernetwork equipment and software to continue to communicate with thisnetwork distributed D-CMRTS units as if it was still a single cable headCMTS (500). Thus, in one embodiment, this computer control system andsoftware that manages the network distributed CMTS will also be called“virtual shelf” hardware and software, because the computer controlsystem may both manage the complex configuration issues involved inrunning a distributed CMTS system, and then shield this complexity fromthe rest of the system when needed. Thus the remainder of the cable headsystem need not be redesigned to handle the distributed CMTSfunctionality, but may continue to address the invention's distributedCMTS as if it was a prior art non-distributed CMTS.

Thus, in some embodiments, the virtual shelf hardware/software systemmay, for example, take as inputs, user demand over multipleneighborhoods for basic TV channels and basic DOCSIS services, userdemand in individual neighborhoods for advanced or premium on-demand TVor premium DOCSIS IP service (IP-on demand), and the limited number oftotal QAM channels that can be carried over cable.

In the first option, the virtual shelf system will simply work usingwhatever empty QAM channels are made available by the cable operator,and will work to optimize data to users within this overall constraint.

In the second option, in order to send still more data, the virtualshelf system may be much more active. It may, for example, elect todirect the QAM modulators in the PHY unit of a head end line card (614)to stop sending signals on one QAM channel (frequency), in order to freeup this QAM channel (frequency) for a neighborhood specific QAM channel(frequency). For this invention, often this process may be taken to anextreme, and the central head end may send out no legacy QAM signalswhatsoever. This frees up a maximal amount of QAM channels forsubsequent neighborhood specific optimization.

In a third option, the virtual shelf system may instruct the D-CMRTSunits to reallocate their neighborhood CATV spectrum or modulationscheme to allow for more upstream data to be transmitted. For example,the D-CMRTS units may work with various CATV cable connected residentialgateways (See FIG. 10) to allocate a greater amount of CATV bandwidth toupstream data.

In either option, the virtual shelf system may instruct the head endGigE PHY (620) units to send neighborhood specific (IP/on-demand data)to those neighborhoods using optical fiber optimized digital datacarrying waveforms, such as GigE waveforms. The virtual shelf system maythen instruct the remote D-CMRTS unit on the fiber node serving thetarget neighborhood to take this IP/on-demand data, decode and QAMmodulate the data using local CMRTS devices (604), and inject this nowRF modulated QAM data on the cable for that particular neighborhoodusing the now empty QAM channels (frequency).

The virtual shelf system can also instruct another remote D-CMRTS uniton a different fiber node serving a different neighborhood to take theIP/on-demand data for this neighborhood from the massive amount ofdownstream GigE data, decode and QAM modulate this data and inject thisnow RF modulated QAM data on the cable for this neighborhood as well.

Note that by this method, even though both neighborhoods may optionally(for backward compatibility) receive some common legacy QAM channels anddata from the head end, the overall CATV QAM channels may not be thesame. Rather, at least for the IP/On-demand data, the same QAM channel(frequency) now carries different data for the two differentneighborhoods.

Using these systems and methods, the effective data carrying capacity ofthe various cables and QAM channels has been increased. Yet, at the sametime, if the centralized computer system (virtual shelf) is properlyconfigured, most of the complexity of the switching arrangement can beselectively hidden from both the upstream (cable head) and downstream(cable modem) systems, thus enabling good backward compatibility withexisting HFC equipment.

As per Ser. No. 12/692,582, in some embodiments, the system may workessentially independently of the legacy CMTS or D-CMTS units at thecable head, and will essentially act to supplement the functionality ofprior art legacy equipment by adding a minimal amount of new equipmentat the cable head.

Here, this new equipment at the cable head cable may consist of variousdigital converters (399) that convert the legacy QAM, FM, QPSK waveformsfor digital output. Other equipment may consist of a media Level 2/3switch (629), a virtual shelf management system (622, 630), andappropriate MAC and PHY devices to send and receive data along opticalfibers. The legacy cable head CMTS may thus continue to operate asbefore (as desired), with the one exception being that the cableoperator should provide for a fair number of empty CATV channels inorder to provide space for the new CATV channels provided by theinvention. In other words, if the cable operator saturates the variousCATV cables with legacy QAM channels, then there will be insufficientCATV bandwidth available to provide much else.

In some embodiments, parts of the system may be embedded into anadvanced D-CMTS (Digital Cable Modem Termination System) head (500) withat least a first packet switch, a first MAC (Media Access Control), anda first PHY (Physical Layer) that optionally may be capable of sendingand receiving data from a layer 2-3 switch to a first end of a firstoptical fiber as at least a plurality of first digitally encoded analogQAM waveforms (first optical signals).

In some embodiments, this first PHY (614) and MAC (612) may be omitted,and instead the D-CMTS head may instead use only a second MAC (618) anda second PHY (620) capable of sending and receiving data from the layer2-3 switch to the optical fiber.

As previously discussed, although in the preferred embodiment, all HFCoptical fiber signals will be sent in a digital format, the system canstill operate in a still higher backward compatible mode. Here abackward compatible wavelength, such as the standard HFC 1310 nmwavelength, may be reserved for prior art analog modulated optical fibersignals (e.g. QAM waveforms) (which may then be digitized for opticalfiber transmission by a converter unit). The invention's digital signalswill then operate on a different wavelength and a second head end PHYmay send and receive data from the IP backbone using this alternateoptical wavelength.

It will often be convenient to send both the legacy (digitized analogmodulated optical fiber signals) data and the advanced data usingsimilar digital protocols (e.g. various IP digital protocols such asGigE). This because then the same switches may be used to handle boththe legacy signals and the advanced functionality signals. This isbecause when all data flows using the same type of digital protocol, asthen simple switches can be used to send relevant data packets to therelevant destinations, and handle these data packets using theappropriate equipment once the data packets reach their intendeddestination.

As previously discussed, although data may be sent and received using asmany optical fiber wavelengths as desired, the invention can reduce thenecessity for using multiple optical fiber wavelengths, and in turnreduce costs.

If backward compatibility is desired, the D-CMRTS fiber node(s) mayoptionally incorporate an external “dumb” digital optical to RF (radiofrequency) conversion device (see FIG. 6, 401) that directly convertsthe digitized versions of the prior art modulated optical signals (sentas QAM waveforms by the CMTS PHY (614) at the first end of the fiber,then digitized by a converter (399), sent over the optical fiberdigitally, and then reconstituted back to copies of the originalwaveforms) to a first set of RF signals. These are typically designatedas O-D/A-E or A-E/O-D (i.e. optical-digital to analog electronic, oranalog electronic to optical digital) converters, depending upon thedirection of the electrical RF to digital fiber optic conversion. Often,however this functionality will be incorporated into the D-CMRTS nodes(e.g. 600, 601, 603, and 605).

In alternate and often more expensive (but higher performance)embodiments where the D-CMRTS (300), (304) unit is designed to operateat a plurality of different optical wavelengths, the units mayincorporate one or more wavelength splitting devices, such as Bragfilters, prisms, gratings, and the like as part of the unit's internalswitch (560), to separate and combine the various optical fiberwavelengths as desired. In some embodiments, these wavelength splittersmay be tunable wavelengths splitters that may operate under softwarecontrol. Although within the scope of the invention, such embodimentstend to be somewhat more expensive due to the costs of the extraequipment. Thus such multiple wavelength embodiments will typically beused more in very high (e.g. demanding) data transport situations.

The D-CMRTS may have at least one (and often a plurality of, e.g. asmany as 160 or more) CATV RF signal generators, such as QAM modulatordevices. These devices will be capable of detecting and encodingselected portions of the digitally encoded optical fiber data intovarious types of RF CATV waveforms. The device's switch (560) may, forexample, be used to sort out digitally sampled legacy RF signals, andsend these to a digital-optical to analog-electrical (RF) converter(600), thus producing copies of the original legacy RF signals. Theswitch may also be used to sort out demodulated legacy QAM signals(waveforms) which contain the underlying QAM symbols, and send these QAMsymbols to QAM modulators (603), thus producing copies of the originallegacy RF QAM symbols by another method. The switch may also be used tohandle IP data packets from the IP backbone connected to the head end,and send these to appropriate QAM modulators (e.g. edge-QAM modulators607 or 604). This later is particularly useful for various video ondemand and DOCSIS applications.

The QAM modulator(s) may be part of a D-CMRTS PHY unit, and the D-CMRTSmay often have the corresponding MAC and packet switching capability, aswell as an optional controller (e.g. microprocessor and associatedsoftware) to select the appropriate portions of the digitally modulatedoptical signals (and wavelengths if necessary) and also control thepacket switching, MAC and PHY (including the D-CMRTS QAM modulators)units as needed.

The D-CMRTS will also usually contain at least one software controllableswitch that can be remotely directed to select at least some of thedigitally encoded optical signals and direct the at least one D-CMRTSQAM modulator devices to encode the selected optically transmitteddigital data into various of RF QAM waveforms at a selected set offrequencies (remotely generated QAM signals). Often this softwarecontrollable switch will be part of, or be controlled by, an optionalprocessor or controller.

The D-CMRTS may also contain at least one remotely software controllableRF packet processor capable of detecting upstream data carried by CATVRF upstream signals generated by at least one cable modem, and digitallyrepackaging and this upstream data and digitally retransmitting thisupstream data along the optical fiber.

The software controllable switch(s) and/or software controllable RFpacket processor(s) may optionally be capable of being remotelyconfigured by software to implement at least a subset of the standardDOCSIS upstream and downstream functions. For example, on the upstreamside, one or more of the DOCSIS upstream Time Division Multiple Access(TDMA) and DOCSIS Synchronous Code Division Multiple Access (SCDMA)functions may be implemented. On the downstream side, one or more of thevarious DOCSIS QAM modulation modes, such as 16-level, 32-level,64-level, 128-level, and 256-level QAM modulation modes may beimplemented. Depending upon the level of functionality of the D-CMRTSthat is desired, the D-CMRTS may, at the fiber node, generate QAMchannels carrying digital broadcast video, digital video on demand,digital High Definition (HD) video, Voice data, and DOCSIS (data)channels.

As previously discussed in Ser. No. 12/692,582, the CMRTS units weredisclosed as being capable of implementing additional functions that arenot yet officially part of the DOCSIS specification (i.e. non-DOCSISfunctionality), such as upstream data from various new models ofnon-DOCSIS standard set-top box gateways, may also be implemented by theD-CMRTS.

Here some of this non-standard functionality is discussed in moredetail. The D-CMRTS unit may often be capable of implementing additionalfunctions that are not yet officially part of the DOCSIS specification(i.e. non-DOCSIS functionality). This additional functionality caninclude ability to handle an increased amount of upstream data fromvarious new models of non-DOCSIS standard set-top box gateways. Asanother example, the D-CMRTS unit may be capable of more intelligentlyallocating the downstream QAM channels depending upon data content needmessages generated by more advanced set top boxes in various households.That is, if a household needs access to a particular video channel, forexample, the household's set top box may send a command to the localD-CMRTS unit requesting this channel. This channel may already beavailable to the D-CMRTS unit because it has access to a vast stream ofdata from the optical fiber connection, but in order to preserve scarceCATV bandwidth, the local D-CMRTS unit will only allocate a CATV QAMchannel for this data upon request. The D-CMRTS unit may also be capableof many other functions as well.

As another example, one persistent problem with CATV cable is that thesignal attenuation properties of the RF signals vary as a function offrequency, as well as the particular characteristics of that stretch ofcable. Lower frequency channels will degrade differently from higherfrequency channels. It is difficult, with the present “one size fitsall” scheme where all QAM channels at all frequencies are generated atthe cable head, to put out a standard CATV signal where all QAM channelsare modulated the same regardless of frequency. By contrast, since aD-CMRTS unit may generate some or all QAM channels locally, it ispossible to use various software adjustable parameters to spectrallyshape the various RF QAM waveforms to adjust for the attenuation overfrequency properties of the that neighborhood's CATV cable. Thus incontrast to prior art methods, where often some of the lower or higherfrequency channels have more noise, it will now be possible to ensurethat all channels have low noise, regardless of the frequency of thechannel.

Thus to an even greater extent than previously discussed in Ser. No.12/692,582, the present disclosure teaches methods that enable a cableprovider to distinguish itself by being able to provide cutting edgeservices that are ahead of its competitors. In this example, the D-CMRTScan be viewed as handling either a superset of the DOCSIS functions or acompletely different set of functions, because it can be used to extendthe functionality of the HFC system far beyond that of the standardDOCSIS functions.

Here the term “superset” is being used to denote the additional(non-standard DOCSIS) functionality. Thus, for example, a D-CMRTS thathas enough backward compatibility to do either a full set of DOCSISfunctions or a subset of DOCSIS functions would be described asimplementing a DOCSIS “superset” if it also implements additionalnon-standard DOCSIS functions. Other examples of additional non-standardDOCSIS functionality (non-DOCSIS functionality) includes functionalityto transmit various forms of digital video such as standard digitalvideo, high definition HD digital video, and various forms of digitalvideo upon demand.

The various D-CMRTS devices will usually have software controllableswitch(s) and software controllable RF packet processor(s), and willoften also incorporate their own microprocessors or microcontrollers, aswell as memory (such as flash memory, ROM, RAM, or other memory storagedevice) to incorporate software needed to operate the switches andprocessors, interpret command packets sent from the virtual shelfmanager, and transmit data packets to the virtual shelf manager.

For greater flexibility, the various D-CMRTS devices may be constructedusing various software reconfigurable Field-programmable gate arrays(FPGA) and Digital signal processor (DSP) devices for their various MACand PHY units, as described in more detail in copending application Ser.No. 13/555,170, “DISTRIBUTED CABLE MODEM TERMINATION SYSTEM WITHSOFTWARE RECONFIGUABLE MAC AND PHY CAPABILITY”, the contents of whichare incorporated herein by reference. These FPGA and DSP units may besoftware reconfigured to enable various types of QAM and othermodulation scheme transmitters and receivers, such as filter banktransmitters and filter bank receivers. These may be constructedfollowing the methods of Harris et. al., (“Digital Receivers andTransmitters Using Polyphase Filter Banks for Wireless Communications”,IEEE Transactions on Microwave Theory and Techniques, 51(4), pages1395-1412, 2003). Other alternative methods may also be used.

The D-CMRTS units will also often have an RF combiner device, or atleast be attached to a combiner device (such as a Diplex or Multiplexdevice), that combines all of the various RF QAM and other CATV signalsto produce a combined RF signal suitable for injection into a CATV cableconnected to at least one cable modem. The diplex or multiplex devicemay also serve as a frequency splitter, or an adjustable frequencysplitter, directing some frequency ranges (e.g. 5-42 MHz for upstreamfunctions, and other frequency ranges (e.g. 54-870 MHz) for downstreamfunctions. These frequency ranges may be adjusted under software controlas desired.

Alternatively, this multiplex device may be external to the actualD-CMRTS unit; however the D-CMRTS unit will normally depend upon eitheran internal or external combiner (e.g. a diplex or multiplex device) forfunctionality.

As previously discussed, the system will also usually have a centralizedcomputer system or computer processor running software (e.g. virtualshelf software) that controls many aspects of its function. Aspreviously discussed, because the prior art (non-dispersed functionally)CMTS units were often referred to as a “shelf”, the computer softwarethat controls the functionality of the dispersed D-CMTS-D-CMRTS units ofthis invention will be referred to in the alternative as a “virtualshelf”. This “virtual shelf” software will ideally manage the muchhigher complexity of the dispersed D-CMTS-D-CMRTS system in a way thatwill be easy to manage, and ideally sometimes almost transparent, to thecable head, so that other systems in the cable head can often handle themore complex data distribution properties of the invention's dispersedD-CMTS-D-CMRTS system as if the system behaved more like a simpler,prior art, CMTS system.

In particular, one important function of the computer processor and“virtual shelf” software will be to select and control at least thedigital optical signals and the remotely generated QAM signals. Thesewill be managed in a way that, as will be discussed, greatly increasesthe amount of IP-on-demand data available for cable system users.

FIG. 1 shows an overall view of the various frequencies and datachannels allocated for prior art CATV systems (100). Typically the lowerfrequencies, such as 5-42 MHz, were allocated for use in transmittingdata “upstream” from the individual cable modems back to the Cable Head(102). Typically upstream data was transmitted using a time-share TDMA(Time Division Multiple Access) manner in which individual cable modemsare allocated certain times on roughly 2 MHz wide QAM channels totransmit data. Starting at around 54 MHz on up to roughly 547 MHz, spacewas allocated for legacy analog video channels (104), which transmit onroughly 6 MHz wide FDM channels. At frequencies above that, frequencies(space, bandwidth) was allocated for digital television transmitting onroughly 6 MHz wide QAM channels (106), and above that, space wasallocated for DOCSIS services (108) that may transmit voice, on-demandvideo, IP, and other information, again generally as a series of 6 MHzwide QAM channels. Above about 1 GHz, cable bandwidth is and was seldomused, although future services may extend further into this region.

The invention is indifferent as to the use of higher frequency cablebandwidth and channels. If available, the invention may use them. If notavailable, the invention will cope with existing cable frequencies andbandwidth.

Prior art CATV cable thus had a finite bandwidth of at most about100-200 downstream QAM channels, and a very limited upstream bandwidth.When this bandwidth is used to serve a large amount of differentcustomized types of data to a large amount of different subscribers,this bandwidth quickly becomes exhausted. Due to the extreme constraintson upstream bandwidth, upstream bandwidth quickly became limiting.

A drawing showing how the prior art CATV spectrum allocation can bedescribed in a more simplified diagram is shown below (110), (120). Thisdiagram will be used in various figures to more clearly show some of theCATV spectrum allocation aspects of the invention, as well as to showhow the invention may deviate from the prior art CATV spectrumallocation on occasion.

The “upstream” segment (112) is an abstraction of all prior art CATVupstream channels, including both presently used upstream channels inthe 5-42 MHz region. The “video” segment (114) is an abstraction of boththe almost obsolete prior art analog TV FDM channels, as well as thestandard “digital video” channels, as well as the projected digitalvideo channels that will occupy the soon to be reclaimed analogbandwidths once the analog channels are phased out. Segment (114) alsorepresents other standard digital radio and FM channels, and in generalmay represent any standardized set of downstream channels that willusually not be customized between different sets of users andneighborhoods.

The “DOC1” channel (116) may be (depending upon mode of use) either afull set or subset of present or future DOCSIS channels. As commonlyused in this specification, DOC1 often represents a basic set of DOCSISservices that would be made available for fallback use by neighborhoodsin the event of a failure of the higher performance IP/on demand or DOC2channels (118). The DOC1 QAM channels are normally chosen so as to notexhaust the full bandwidth of the CATV cable, so that at least someremaining QAM channels are available for the neighborhood customizedDOC2 channels. The “IP/On-demand or DOC2” channel (118) is essentially(depending upon mode of use) the remaining available downstreambandwidth on the CATV cable, and is usually reserved for transmittingneighborhood specific data (IP/On-demand data), often transported by adifferent communications media (such as a second fiber or secondwavelength, and often by a non-QAM protocol) from the cable head toindividual neighborhoods.

Note that when discussing prior art usage, the sum of the DOC1 (116) andIP/On demand (118) channels sent by optical fiber to a group ofneighborhoods can never (or at least should not ever to avoidinterference) exceed the effective bandwidth (i.e. the carrying abilityof the CATV cable and the ability of cable modems to detect the cable RFsignal) of the CATV cable.

By contrast, when discussing the invention, the sum of the DOC1 (116)and IP/On-demand (118) channels sent by optical fiber to a group ofneighborhoods will often exceed the effective bandwidth of the CATVcable on a group of neighborhoods basis, although the sum of DOC1 (116)and IP/On-demand (118) will never exceed the effective bandwidth of theCATV cable on a per-neighborhood basis.

If the same CATV spectrum is transmitted by optical methods (i.e.optical fiber), so that the same waveforms are transmitted at the samefrequency spacing, but simply transposed to optical wavelengths, thenthis spectrum will be designated as (120), but the various waveformswill otherwise keep the same nomenclature to minimize confusion.

In many embodiments, the invention may intentionally deviate from thisprior art CATV spectrum allocation scheme. In particular, as will bediscussed, the amount of bandwidth reserved for upstream data may besubstantially increased. This may be done by, for example, deviatingfrom the traditional 4-42 MHz region reserved for upstream data, andallocating a larger number of CATV RF frequencies for upstream data.

FIG. 2 shows an overall view of the various wavelengths allocated forboth prior art optical fiber wavelength division multiplexing schemes,as compared to the dense wavelength division multiplexing (DWDM) methodswhich may optionally be used in some embodiments of the presentinvention. Here the optical fiber wavelengths being used at present(150) include a 1310 nm O-band wavelength (152) often used to transmitthe various CATV RF channels, such as the various QAM channels,modulated essentially according to the same CATV RF waveforms, but atoptical wavelengths according to scheme (120). Supplemental data isoften transmitted in the C-band around 1550 nm (154), often on opticalwavelengths and waveforms that, because the waveforms are modulatedaccording to non-optimal CATV waveforms, must be separated from eachother by a relatively large wavelength separation, and which carrysub-optimal amounts of data per wavelength.

By contrast, if all data is transmitted according to the same digitalformat, such as an IP based GigE format, then it becomes relativelysimple to label any type of data as to data type and data destination,dump it in the optical fiber digital stream at the same opticalwavelength (170), and then extract the digital data at the other end ofthe optical fiber, sort by data type and destination, and send it to theproper recipient. This all digital approach thus can have advantagesover DWDM methods because the DWDM costs of producing optical modulators(e.g. optical fiber lasers) as well as demodulators, wavelengthsplitters, and the like, thus can be reduced.

Although the present invention, by virtue of the fact that all data willusually be transmitted digital form over the optical fiber, thus doesnot require use of dense wavelength division multiplexing (DWDM)methods, it is useful to briefly examine such DWDM methods because theymake the advantages of the present invention's all digital approach moreapparent.

The Dense Wavelength Division Multiplexing (DWDM) concept is shown in(160). Parent provisional applications 61/385,125 and 61/511,395, thecontents of which are incorporated herein by reference, taught thatbackward compatible downstream legacy signals might be transmitted inanalog form using, for example, a legacy O-band analog signal, andadditional channels and services might be transmitted at multiplewavelengths using more efficiently modulated data signals (such as oneof the various optical fiber GigE protocols), for example as a series ofclosely spaced wavelengths (162). These provisional applications alsotaught that due to the fact that because use of prior art QAM, NTSC, FMwaveforms and the like, when used on optical fiber, is relativelyinefficient, on a bits of data per unit bandwidth basis, compared tomore modern digital methods of transmitting data, use of digital signaltransmission methods offered compelling differences in data transmissionrates.

Specifically, whereas prior QAM, NTSC, FM waveform methods might, forexample, be used to transmit 4 C-band wavelengths, each carrying about 6gigabits per second of data, using CATV compatible QAM, NTSC, FMwaveforms (154), by switching to digital methods, much higher datarates, such as up to 80 wavelengths of C-band data (162), each carrying10-100 gigabits of data per second, are possible using more efficientoptical fiber signal modulation methods.

The present invention thus builds on this earlier insight, and is basedon the further insight that by completely digitizing all optical fibertraffic (e.g. removing the legacy analog waveform optical fibertraffic), intelligently compressing as possible (e.g. using QAM symboldemodulation methods) and going all digital, then on a bits per secondbasis, much more data may be transmitted using fewer opticalwavelengths, thus saving the costs of the extra equipment needed tohandle the extra optical wavelengths.

Note however that the present invention still may make use of DWDMmethods when, for example, extremely high data transmission rates (bitsper second) are desired. However in the present invention, use of alldigital optical fiber transmission is now the preferred embodiment, anduse of DWDM methods is an optional element that is not required topractice the invention, although it may be.

To help visualize how switching to an all digital optical fibertransport format can help transmit more data over even a single opticalfiber wavelength, the simplified digital transmission diagram (170) or(306) is frequently used. Note that a legacy 0 band analog modulatedoptical signals (152) or C band optical signals (154) can carry only atmost about 6 Gigabits per second (Gbit/s), with an effective bit ratemuch less than this due to the inefficiencies of the analog format. Bycontrast, the more efficient digital format can transmit 10 Gbits/secondor more at the same wavelength, and here the effective bit rate is veryclose to the theoretical bit rate. The net effect is that by switchingto an all digital mode, the same wavelength on the optical fiber can nowtransmit much more data than it could earlier.

FIG. 3 shows a simplified version of how prior art HFC systems (200)transmit data from the cable head (202) to different optical fiber nodes(204) serving different neighborhoods (206). Each neighborhood willtypically consist of up to several hundred different houses, apartments,offices or stores (208) (here referred to generically as “houses”), eachequipped with their own cable modems (not shown). Here, for simplicity,only the downstream portion of the HFC system is shown.

The cable head will generally be connected to an IP backbone (212)and/or will obtain standardized media content (210) (such as a standardassortment of analog and digital video channels) from one set ofsources, and also obtain more individualized data (212), such as videoon demand, IP from the IP backbone which may include both the internet,and other individualized data from other sources. This data is compiledinto a large number of different QAM (and at present also FDM) modulatedCATV broadcast channels at the CTMS shelf (214). This CMTS (214) willoften have a number of different blade-like line cards (216). These linecards transmit the signals by optical fibers (218) to different areas(groups of neighborhoods).

Note that the FDM modulated CATV broadcast signal is an NTSC analogsignal (for older style analog televisions), and even the QAM signal,although it carries digitally encoded information, is itself an analogsignal as well. For historical reasons, in the downstream direction,both FDM/NTSC and QAM waveforms (signals) usually have a bandwidth ofabout 6 MHz in the US.

To show this, as previously discussed in FIG. 1, the FDM/NTSC and QAMsignals are shown as having a center wavelength and bandwidth in orderto emphasize the essentially analog nature of this signal, even whencarrying digital information. These analog signals can be carried byoptical fibers, and converted into RF signals for the CATV cable part ofthe network, using very simple and inexpensive equipment.

As previously discussed, typical HFC networks actually have a rathercomplex topology. Rather than sending one optical fiber from the CTMS toeach different neighborhood, typically optical fibers will servemultiple neighborhoods. To do this, the signal from the CTMS sideoptical fiber will at least usually be split (by an optical fibersplitter (220)) into several different optical sub-fibers (222), andeach sub-fiber in turn will in turn carry the signal to a differentfiber optic node (fiber node, FN) (204). Here the rather complex ringtopology of HFC networks will be simplified and instead represented bythese fiber splitters.

At the fiber node (FN) (204), the optical signal is converted into aCATV radio frequency (RF) signal and sent via CATV cables (226) toindividual cable modems at individual houses (208) in each neighborhood.Typically each neighborhood will consist of 25 to several hundredhouses, served by a CATV cable (226) that connects to the local fibernode (204).

Since the CATV cable (226) is connected to all of the houses (208) inthe neighborhood (206), if the cable modem in one house in aneighborhood wants to request customized on-demand video or IP, then allof the houses in the neighborhood that are attached to that particularCATV cable will actually receive the customized signal. Although onlythe cable modem associated with the requesting house (not shown) willactually tune into and decode the requested signal, it should beappreciated that if each individual house in the neighborhood were tosimultaneously request its own customized set of video on demand or IPat the same time, the limited bandwidth of the CATV cable would berapidly saturated. As a result, there is an upper end to the amount ofcustomized data that can be transmitted to each house, beyond whichbandwidth must be limited and/or requests for additional customized datawill have to be denied.

Although the different blades or line cards (216) of the CMTS shelf(214) at the cable head (202) can send different customized IP/on-demandchannels to different groups of neighborhoods, the granularity of thisprocess is sub-optimal, because all individual neighborhoods connectedto the same fiber splitter will get the same customized IP/on-demandsignal. Given the limited bandwidth of the CATV cable, if allneighborhoods get the same signal, then the amount of data that can besent to each individual neighborhood must, by necessity, be limited soas not to exceed the total available bandwidth.

FIG. 4 contrasts the difference in downstream data transmission betweena prior art HFC system that operates using an optical fiber carrying ananalog CATV modulated 1310 nm wavelength signal, and the invention'simproved digital methods using digital (Ethernet) modulated signals.

In the prior art system, the conversion process between the opticalfiber (222) and the CATV cable (226) that occurs with a typical priorart fiber node (204) is shown, and contrasted with the invention'simproved D-CMRTS fiber node (300). Here, for simplicity, only thedownstream portion of the process is illustrated.

In the prior art conversion process (top), the optical fiber (222)carries both the standardized video signals, and the analog QAM signal(that contains digital information) for both digital television andDOCSIS use (that can carry on demand video or IP data).

The prior art “dumb” fiber node (204) simply converts the opticalfiber's optical FDM or QAM analog signals into RF FDM or QAM signals andpasses these signals to the CATV cable (226). Thus if, for example,there are four different CATV cables connecting to this different fibernode, all will get the same customized IP/On-demand signal, and this inturn may be rather inefficiently transmitted to potentially thousands ofnon-target households that did not request the customized signal.

By contrast, by using the invention's improved “smart” D-CMRTS fibernodes (300), any legacy standardized signal (e.g. the standardized videochannels) and (for backwards compatibility) either a full set or subsetof the DOCSIS QAM channels are first digitized and transmitted by theoptical fiber in a digital format. This digital format makes it easy toadd additional (non-legacy) data (e.g. video on the demand, DOCSISsuperset services) and transmit this additional data on the same opticalfiber wavelengths used to transmit any legacy CATV data.

If legacy data is transmitted over the optical fiber, it may optionallycarry a digitally encoded version of the legacy CATV spectrum, which canbe reconstituted (320) into analog format at the D-CMRTS unit into RFQAM waveforms and other waveforms that may optionally be injected intothe CATV cable (120) for fallback or legacy operation.

To emphasize the fact that the optical fiber is often carrying data bynon-CATV-compatible or QAM signal carrying methods, the signal carriedby the D-CMRTS fiber is shown as a series of lines (306) to symbolizethe fact, that alternative digital (e.g. GigE) methods of signaltransmission are being used. Here each line (306) represents a differenttype of data stream to different node addresses or different nodechannels or CATV waveforms, some of which will ultimately will beconverted to a QAM signal and sent to a specific neighborhood.

At the invention's improved D-CMRTS fiber node (300), the fiber node'sCMRTS unit will determine (or at least select) which set of customizeddata carried by the various optical fiber digital packets (307, 308,310, 312) is intended for that particular D-CMRTS and neighborhood, andretrieve this information from the fiber. This information will then beQAM modulated and converted to the appropriate RF frequency, put onto asuitable empty IP/On-demand QAM CATV cable channel (314), (316), (318),and then sent by CATV cable to the neighborhood that requested thatparticular data. At the neighborhood, the particular cable modem fromthe house that requested that data can tune into this QAM channel andextract the data, while the other cable modems also attached to thatcable will ignore the QAM channel and/or ignore the data.

As can be seen, the digital data packets (306) carrying different typesof data can be selected and put onto the CATV cable in various mix andmatch combinations (316), (318) as desired. Here for example, one RF QAMchannel on (316) came from optical fiber data packet type (310), two RFQAM channels came from optical fiber data packet type (312), and one RFQAM channel came optical fiber data packet type (308). By contrast, for(318), two RF QAM channels came from optical fiber data packet type(310), one RF QAM channel came from optical fiber data packet type(308), and one RF QAM channel came from optical fiber data type (312).By contrast, (314) illustrates the CATV channel coming from aneighborhood that is operating in legacy mode, where all channels camefrom optical fiber data packets from digitally sampled or demodulated(320) legacy RF signals (120) that were simply transported, in digitalformat, as is and then reconstituted (320) back to the originalwaveforms at the D-CMRTS fiber node (300), or alternatively by a simpleroptical digital to RF analog converter type optical fiber node.

As will be discussed shortly, this method allows for much finergranularity, and a correspondingly higher rate of transmission ofcustomized data.

As previously discussed, according to the invention the upstream datatransmission bottleneck at the CATV cable may be also addressed by anupstream CATV bandwidth reallocation scheme (See FIG. 10, (390)). Here,the amount of CATV RF spectrum allocated to upstream data transmissionmay, for example, be increased—e.g. from the original 5-42 MHz range upto, for example, 5-547 MHz or other higher upper value.

FIG. 5 shows an overview of one embodiment of the invention in operationin downstream mode. Here, in this embodiment, the improved “smart”D-CMRTS fiber nodes (300) can transport a higher effective amount ofcustomized user data. Here these improved “smart” D-CMRTS fiber nodes(300), may in some embodiments, work in conjunction with optionalimproved D-CMTS shelf and improved D-CMTS line cards at the cable head(see FIG. 7, 500).

In this embodiment, any legacy CATV RF waveforms, such as QAM waveforms(120), produced at the head end (202) may be digitized by a converterunit (399) and then injected into the optical fiber (301). Thisconverter unit (399) may function by, for example, being configured toaccept at least one of downstream RF waveforms and downstream QAMchannels from the head end, sample and digitize the downstream RFwaveforms (e.g. using simple high speed analog to digital conversion)and/or demodulate the downstream QAM channels into QAM symbols,producing downstream digital QAM symbols. In this embodiment, theconverter (399) is then digitally encoding the digitized legacy datainto a suitable optical fiber digital transport format, such as GigEdata packets, and then injecting these data packets into optical fiber(301) along with other data.

In the prior art system example previously shown in FIG. 3, an opticalfiber (218) from the prior art CMTS unit (214) at the cable head wassplit at by a fiber splitter (220) into three sub-optical fibers (allcarrying the same data) (222), and these sub-optical fibers were thenrouted to three different neighborhoods. Because all optical fiberscoming from the fiber splitter will carry the same data, all data,including customized data, is inefficiently sent to all threeneighborhoods, even though only one house from one neighborhood may haveactually requested the customized data.

As a result, the limited carrying capacity (bandwidth) of the prior artCATV cable system rapidly becomes saturated.

By contrast, by using an improved head end D-CMTS shelf (500) withimproved D-CMTS line cards, and the present invention's digitaltransmission methods, larger amounts of downstream data can be sent evenwhile using the same number of prior art optical fiber wavelengths.Again, the key concept is to use more efficiently modulated opticalfiber digital data transport protocols, such as higher data capacityGigE modulation protocols (304).

On the way to the various neighborhoods, or at the variousneighborhoods, the optical fiber cable and/or CATV cable data signalsmay optionally pass through a digital switch (220D). Here theinvention's present use of all digital transmission methods providesadvantages over the previously proposed DWDM methods.

Under DWDM methods, data to different optical fiber nodes, or multipleoptical fiber node devices, might be transmitted at differentwavelengths, requiring that the switch (220) be a smart fiber splitterthat might, for example, incorporate rather expensive optical devices,such as software controllable Brag filters, that would operate toseparate out the various optical fiber wavelengths and divert them todifferent neighborhoods as needed.

By contrast, by using digital transport methods, digital switch (220D)can be a relatively inexpensive multiple port switch that operates todirect the various digital data packets to their respective destinationsaccording to digital data packet headers, and the like.

To do this, typically the various DOFN or D-CMRTS units will have aprocessor, memory, and at least one address (e.g. the specific nodeaddress, and or one or more alternate addresses such as the address of agroup of nodes, useful for when broadcasting the same signal to multiplenodes is desired). The DOFN or D-CMRTS units will typically beconfigured to process downstream digital data that is directed to theirrespective addresses.

Here, also, the IP data packets (e.g. digital samples of downstream RFwaveforms, downstream digital QAM symbols, or downstream digital IPdata) transmitted over the optical fiber will often have a specific(e.g. individual node or group of nodes) digital optical fiber nodeaddress.

In some embodiments, digital switch (220D) may be a multiple port switchdisposed either at the head end or else somewhere between the head endand the various digital optical fiber nodes (D-CMRTS units). This switch(220D) can thus be configured to read the specific digital optical fibernode or D-CMRTS addresses; and direct any of the various digital samplesof downstream RF waveforms, downstream digital QAM symbols, ordownstream digital IP data to the specific digital optical fiber node ornodes corresponding to their specific digital optical fiber nodeaddress, be it individual node address, or specific group of nodesaddress.

Here, use of all digital methods also helps cost reduce the variousD-CMRTS. Whereas under the prior DWDM scheme, the various D-CMRTS unitsthemselves may have extracted data from multiple optical fiberwavelengths through us of more expensive wavelength splitters (such assoftware controllable Brag filters), use of digital data packets makesuse of such wavelength splitters optional. Under the present all digitalscheme, the various D-CMRTS units can essentially pick and choose whatGigE formatted data they may need from the overall digital data packetstream (306, 307, 308, 310, 312) extract this data, reconstitute,remodulate, or QAM modulate the various data types, and then output CATVRF signals (again often QAM channels) that can be a composite of thedata originally carried on the different digital data streams (307, 308,310, 312).

This “mix and match” process is symbolized by the various dark, dashed,and dotted parabolas shown in (316) and (318), which symbolize the CATVRF modulated data that is being output in neighborhood 1 andneighborhood 2 by D-CMRTS Fiber Node 1 and DCMRTS Fiber Node 2. Here forexample, as before, the downstream CATV data (226), (316) onneighborhood 1 is shown as a mix of dark parabolas (data originallyobtained from fiber digital data packets (310), a mix of dashedparabolas (data originally obtained from fiber digital data packets308), and dark dotted parabolas (data originally obtained from fiberdigital data packets 312). Note that the mix of data for neighborhood 2(318) is different from neighborhood 1. Whereas neighborhood 1 only tooka small amount of data (dark parabola) from fiber digital data packets(310), and a larger amount of data (two dark dotted parabola) from fiberdigital data packets (312), here the D-CMRTS unit (300) for neighborhood2 has selected more data (two dark parabolas) from fiber digital datapackets (310), and less data from (one dark dotted parabola) from fiberdigital data packets (310).

Note also that the D-CMRTS unit has freedom to decide what frequencieswill be used to transmit this data over the CATV cables. Here theD-CMRTS units determine what data to place on the neighborhood CATVcables based upon commands sent upstream by the various householddevices attached to the CATV cable, and/or commands sent from the cablehead. As previously discussed, often the D-CMRTS optical fiber nodeswill be software controlled.

Due to this software controllable, neighborhood specific (or at leastneighborhood region specific) ability to combine and repackage hugeamounts of GigE formatted data carried over a large number of opticalfiber channels, the downstream capability of the system can now besubstantially higher than prior art HFC systems.

Note also that some backward compatibility can be preserved, if desired.Here, for example, fiber digital data packets (307) can still be used todigitally transmit the legacy CATV RF signals, such as QAM signals. Thiscan be done by having converter (399) intercept the legacy signals,digitize them by a relatively “dumb” Analog-RF to Digital Optical units,or by demodulating the QAM waveforms, extracting the QAM symbols, andthen transmitting the QAM symbols in a digital format.

These digitized legacy signals can continue to be sent to “dumb” opticalfiber nodes (204), and the digital optical data reconstituted (e.g. byoptical-digital to analog-RF units, or by feeding the digital QAMsymbols into local QAM modulators). Both operations can be done withminimal onboard intelligence at the optical fiber node, hence the “dumb”label. This “dumb” optical fiber

In FIG. 5, neighborhoods 1 and 2 are served by the invention's improved“smart” D-CMRTS fiber nodes (300). By contrast, neighborhood 3 is onlyserved by a “dumb” fiber node (204).

FIG. 6 shows one embodiment of the invention operating to send dataupstream. As previously discussed, at the CATV cable, considerably moreupstream data can be sent due to the previously discussed (but optional)methods of allocating more CATV bandwidth for upstream data (e.g. usingspectrum reallocation). Because spectrum reallocation is easier to draw,this larger amount of upstream data being transmitted along the CATVcable is symbolized here by the two dark dotted or dashed parabolaslabeled “upstream data” for neighborhoods 1 and 2, showing the higheramounts of upstream spectrum. By contrast, the smaller amount ofupstream data that can be transmitted using prior art methods issymbolized by the one dark parabola labeled “upstream data” forneighborhood 3. Here for example, perhaps neighborhood 3 is using thestandard US CATV upstream partition that allocates 5-42 MHz for upstreamdata, while neighborhoods 1 and 2 are using an alternate scheme such asallocating 5-85 MHz for CATV upstream data. Here for example, RFmultiplexer or diplex (606) can be switched into an alternate mode thatdeviates from the present 5-42 MHz upstream and 54-870 MHz downstreamstandards, and instead allocates the 5-85 MHz region for upstream, andfor example the 92-870 MHz region for downstream.

As previously discussed, if the higher amount of upstream data wassimply transmitted back along the optical fiber system using the sameinefficient (for optical fiber) CATV signal modulation scheme (againusually QAM modulation), then the optical fiber itself would rapidlybecome a rate-limiting bottleneck. To avoid this problem, according tothe invention, the D-CMRTS nodes may extract this upstream data, andrepackage it into more efficiently (for optical fiber) modulated GigEformats. Additionally or alternatively, according to the invention,digital switches (220D) or smart fiber combiners (220) may themselvestake the upstream data sent by the optical fibers (222) connectingvarious neighborhoods, and extract the upstream data and repackage theupstream data in a more efficiently modulated (for optical fiber) GigEformat.

Although much of the upstream content consists of relatively standardQAM waveforms, at least some legacy CATV systems can also provide avariety of unusual upstream RF waveforms, such as various QPSK channelsfrom various older set top boxes, and the like. However it is burdensometo try to parse each and every possible upstream waveform for content.To avoid this burden, here again more general methods that simplydigitize whatever waveform is seen can be useful.

Thus to be able to digitize, and optically transport upstream, apossibly wide variety of possible RF CATV waveforms, while at the sametime trying to conserve optical fiber bandwidth where feasible, in someembodiments, the digital optical fiber node (D-CMRTS unit) willadditionally have at least one of:

1: An RF digital converter device configured to accept upstream RFwaveforms transmitted over the CATV cable, and digitize these upstreamRF waveforms using, for example, a high speed analog to digitalconverter, and produce digitally encoded upstream RF channel data.2: Since many upstream RF signals will be QAM waveforms, for opticalfiber bandwidth efficiency purpose, it is often desirable to also havean RF demodulator device configured to accept upstream RF QAM channelstransmitted over the CATV cable, and demodulate the RF QAM channels andproduce the upstream digital QAM symbols that originally were used toconstruct the various upstream QAM waveforms.3: Additionally, for high performance, it is also often desirable tohave a QAM to IP conversion device configured to accept upstream digitalIP data packets transmitted by the upstream QAM RF channels over theCATV cable, and extract said upstream digital IP data packets, thusproducing upstream digital IP packets.

Once this digital data has been produced, the digital optical fiber nodeor D-CMRTS unit will also often have a digital data to optical converterdevice configured to combine any of these digitally encoded upstream RFchannel data, upstream digital QAM symbols, and upstream digital IPpackets and transmit this data, symbols, and packets digitally upstreamover the optical fiber.

More specifically, note that the D-CMRTS units themselves may, in someembodiments, use relatively simple digitization methods, such asRF-analog to optical-digital converters, or QAM demodulators, to extractupstream CATV RF signals, digitize them, and transmit them in a fiberdigital format such as GigE back to the head end. Here again, by simplygiving the data packets an appropriate label or header, it is relativelysimple to aggregate data from many D-CMRTS units, and send them all backupstream on the same optical fiber channel (as desired), again bothincreasing upstream data handing capability and also saving costs overalternative methods.

Thus in FIG. 6, the large amount of upstream data from neighborhood 1(400, dark dotted parabolas) and the large amount of upstream data fromneighborhood 2 (402, dark dashed parabolas), could in alternativeschemes have originally been sent upstream along optical fiber (222) byD-CMRTS Fiber Node 1 and D-CMRTS Fiber Node 2 (300) at various differentoptical fiber wavelengths to avoid interference.

However, since, according to the invention the D-CMRTS units may haveeither repackaged and remodulated this upstream data into a moreefficient more optical fiber transmission GigE format, this data fromdifferent neighborhoods may instead be sent back using the same opticalfiber wavelength (if this option is desired, which it often may bebecause it is cheaper).

Note that although this disclosure has focused on the all digitaloptical fiber transmission aspects of the invention, this focus shouldnot be intended to exclude the fact that analog optical fibertransmissions may also co-exist along optical fiber (222).

Consider the case for neighborhood 3. In some schemes the D-CMTRS unitsor a prior art dumb fiber node (204) may simply and relativelypassively, have transuded the upstream CATV RF waveforms from RF tooptical signals such as infrared optical signals, and then retransmittedthe upstream data otherwise modulated “as is”.

Although this option is not excluded, in a preferred embodiment, thedumb optical fiber node (204) may either be replaced by a dumb digitalconverter optical fiber node that does little more than digitize theupstream CATV RF signal (e.g. using a module such as 601 or 605), andtransmit this digital data upstream on optical fiber (222) according tostandard optical fiber digital formats. As yet another embodiment, theprior art dumb optical fiber node (204) may be retained, but a digitalnode converter unit (401) may be put in place to convert optical fibersignals back and forth between a digital format and a legacy analogformat for the legacy dumb optical fiber node (204). Here, this nodeconverter unit (401) may, in some embodiments, essentially do the sametype of data repackaging and remodulation functions of previous switch(220) previously discussed in parent provisional applications 61/385,125and 61/511,395, the contents of which are incorporated herein byreference.

In the present disclosure, switch (220) is instead operating as a multiport digital data switch (220D), which may operate at either onewavelength or a plurality of wavelengths as desired, and the dataextraction, digitization or reconstitution functions, and analog formatto digital data packet repacking functions may instead be moved to otherdevices such as converters (399) and (401).

For example, in this scheme, the upstream data from neighborhood 1 (darkdotted parabolas) and the upstream data from neighborhood 2 (dark dashedparabolas) has been digitized and repackaged by the D-CMRTS units (200)into various digital data packets.

Without such digital conversion, the two upstream data sources may havebeen originally sent by the various D-CMRTS units on different opticalwavelengths. But because the data has now been repackaged at the D-CMRTSunits, now the data from both neighborhoods can be carried upstream onoptical fiber digital data streams (308) and (312) at the samewavelength along optical fiber (301).

FIG. 7 shows a more detailed view of how the D-CMRTS fiber nodes (300),converters (399) and improved digital cable modem termination systems(D-CMTS) (500) at the cable head with improved D-CMTS line cards, mayoperate.

For simplicity, again primarily the downstream portion of the system isshown. Generally the D-CMRTS units will have an onboard digital dataswitch (560) (operating either with optical fiber digital data packets,the electrical version of these optical fiber digital data packets) usedto direct various optical fiber data packets to and from their correctdestination devices (e.g. 600, 601, 603, 604, 605, 607) inside theD-CMRTS.

Although a capability of operating at multiple optical wavelengths isnot required, in an alternative embodiment where operating with aplurality of optical fiber wavelengths is desired, then the switch (560)may optionally also include optical fiber wavelength splitters, such asone or more Brag filters or other device, to separate out the variouswavelengths. These optical fiber wavelength splitters may optionally bea “smart” or tunable filter that may select different wavelengths undermicroprocessor and software control. The different wavelengths selectedby this splitter may then be sent to various subsystems, such as CMRTSunits (604), which can extract the digital data, repackage it, andgenerate CATV QAM signals and/or other RF signals for the CATV cable.

For backward compatibility, the D-CMRTS fiber nodes (300), (304) mayalso have one or more simple optical-digital to analog RF (O-D/A-RF)(600) converters to convert any digitized legacy downstream opticalfiber data, which may contain analog to digital sampled versions ofvarious CATV NTSC, FM, QPSK, or even QAM waveforms back from digitaldata packets to their respective analog RF waveforms again. Depending onthe embodiment, (O-D/A-RF) converters may work directly on downstreamoptical data, or alternatively work on electrical equivalents of thedownstream optical data signals.

The D-CMRTS fiber nodes may additionally contain the reverse upstreamversions of these units (601). These upstream units will take selectedupstream RF signals from the CATV cable, such as set top box QPSKchannels or even DOCSIS upstream channels as needed, do an analog todigital conversion, fit into data packets, and optionally eithertransduce into upstream optical data packets, or allow a later stagedevice such as switch (560) to transduce into upstream optical datapackets to send back to the head end.

Also for backward compatibility, the D-CMRTS fiber nodes (300), (304)may also have one or more QAM remodulator devices (603) to takedemodulated QAM symbols from the downstream optical data packets, andconvert these back into RF QAM waveforms carrying the same data payload,and then send downstream on the CATV system via diplex or RF demodulator(606). Again depending on the embodiment, these QAM remodulator devicesmay work directly on optical data, or alternatively work on electricalequivalents of the optical data signals.

These QAM remodulator devices may additionally contain the reverseupstream RF QAM demodulator versions of these units (605). Theseupstream QAM demodulator units may take selected upstream QAM RF signalsfrom the CATV cable, such as various legacy DOCSIS upstream QAM channelsas needed, demodulate the RF QAM waveforms to extract the underlying QAMsymbols that generated the waveforms, fit these demodulated upstream QAMsymbols into data packets, and optionally either transduce these QAMsymbols into upstream QAM symbol optical data packets, or allow a laterstage device such as switch (560) to transduce into upstream QAM symboloptical data packets to send back to the head end.

The D-CMRTS units may additionally contain one or more optical datapackets (e.g. optical IP data packets) to RF QAM waveform converters(607). These IP to QAM converters are useful for, example, convertinglegacy broadcast QAM channels from the head end that have beendemodulated at the head end and packaged into optical data packets formore compact (e.g. lower bandwidth needed) transport over the opticalfiber than would be possible than if the entire legacy head end analogQAM channel waveforms had instead been transposed to equivalent opticalQAM waveforms. In some embodiments (not shown), the D-CMRTS units mayalso contain the reverse version of these units that takes upstream QAMRF data, demodulates it, repackages the upstream QAM symbols into IPdata packets for optical upstream transmission.

The D-CMRTS fiber node (304) will also contain one or more CMRTS units(604) that will select at least some of the GigE formatted data (310),(310), (307) from the optical fiber (222) QAM modulate this data, andsend it to the CATV cable. (226) according to the scheme previouslydiscussed in FIG. 4. The CMRTS (604) portion of the D-CMRTS unit (304)may in some embodiments generally function as previously discussed incopending application Ser. No. 12/692,582, the contents of which areincorporated herein by reference.

It should be appreciated that this mix and match system will impose aconsiderable configuration and management problem on the D-CMTS units atthe cable head (202). As previously discussed in parent application Ser.No. 12/692,582 and also in the present specification, this complexitymay be handled by a computerized network management system and softwaretermed the “virtual shelf”.

In one embodiment of the improved “virtual shelf” system, the D-CMTSshelf and improved D-CMTS line cards may optionally be configured withboth packet processors (610), and MAC (612) and PHY (614) devices orfunctionality to transmit standard CATV analog, QAM, NTSC, QPSK, andDOCSIS analog signals, where the signals may be digitized by converter(399) and transported over the optical fiber as a series of legacyoptical IP data packets (307).

The same CMTS shelf and line cards may also be configured with packetprocessors (616), MAC (618) and PHY (620) functionality to some or allof this data as GigE formatted data as various digital optical IP datastreams (e.g. 308, 310, 312) on one or optical fiber wavelengths.

As a result, the MAC (618) and PHY (620) for (308, 310, 312) can bedifferent from the MAC (612) and PHY (614) used for the optical fiber IPdata packets for the legacy signals (307).

The exact mix of signals transmitted and received by the improved linecard will vary depending upon what sort of fiber nodes are connecteddownstream (southern end) to the line card.

For example, if all of the fiber nodes were “dumb” prior art fiber nodes(204), then the D-CMTS line card may only transmit legacy digitizedoptical IP data packets (307), and after passing through converter (399)the functionality of that particular D-CMTS line card could be backwardcompatible with prior art CATV DOCSIS equipment and fiber nodes.

That is, the optical fiber legacy IP data stream (307) could transmitthe full set of DOCSIS channels, simply by brute force analog todigital, digital optical transmission, and digital to analog conversion;and/or brute force QAM demodulation into QAM symbols, digital opticaltransmission, and QAM symbol remodulation back into QAM waveformmethods.

By contrast, if all of the fiber nodes were “smart” improved D-CMRTSfiber nodes (300), then the improved head end D-CMTS and CMRTS line cardmight elect to maximize all or nearly all data to the various householdsby skipping legacy mode, just sending all data via the non legacyoptical IP data packets (308, 310, 312) one or more wavelengths in anoptical digital transport protocol such as GigE format, and leave it tothe D-CMRTS units (300), (304) to then handle the reformatting andconversion to CATV RF modulation schemes such as QAM modulation.

This scheme would thus allow the highest amount of customized data to besent to the houses on that particular stretch of cable.

In a mixed mode HFC system using a mix of “dumb” fiber nodes (204) and“smart” CMRTS fiber nodes (300) (as previously shown in FIG. 5), theimproved D-CMTS and D-CMTS line cards could ideally elect to operate inboth legacy and GigE modes, thus transmitting and receiving standardvideo channels (114) and DOCSIS (116) information to and fromneighborhood 3 (served by the “dumb” fiber node), using the digitalconverter (399), optical node converter (401), and the legacy opticalfiber digital IP packet data stream (307) to continue giving adequateservice to neighborhood 3.

As previously discussed, in order to manage this complexity, thefunctionality of the improved head end D-CMTS and D-CMTS line cards, aswell as usually the functionality of the D-CMRTS fiber nodes (300), maybe extended by use of additional “virtual shelf” network managementcomputers, controllers, and software.

In one embodiment, a unified network management system (exemplified by,for example, the ConfD management system provided by Tail-fincorporated) is added to the improved D-CMTS and line card to unify thenetwork and D-CMTS hardware and virtualization layer, provide operatingsystem services, manage middleware, and configure the system to use theproper networking protocols. In this embodiment, all or at least muchnetwork configuration data is stored on a database in the D-CMTSmanager, and the configuration of the network is controlled by a processin which the management software (ConfD) communicates over IPC (sockets)with apps that control the function of various packet processors, MAC,and PHY devices on the improved D-CMTS and D-CMRTS units.

Here the a computer or processor and associated software memory (622)are shown directly controlling the operation of an improved D-CMTS unitby way of various other controllers (624), (626) located in the improvedD-CMTS backbone and line cards (500). The communications between this“virtual shelf manager” (622) and the local controller processors (624),(626) are shown as dashed lines (628). The virtual shelf manager mayalso control the operation of a level 2/3 switch (629) and/or otherdevices that connect the improved D-CMTS unit to the media content(210), IP backbone “cloud” (212), and other services provided by thecable head (202).

The virtual shelf manager may often also manage the configuration of thevarious “smart” D-CMRTS fiber nodes (300), often by communicating withcontrollers and applications software embedded with the D-CMRTS fibernodes (not shown). Given the typically long distances between theD-CMRTS fiber nodes (300) and the virtual shelf manager (622) andimproved D-CMRT (500) (which will often be located at the cable head,miles or more away from the various nodes (300)), the D-CMRTS fiber node(300) to virtual shelf manager (622) communication will often be done byvarious signals and signal protocols communicated by the optical fiberor fibers. In one preferred embodiment, socket based inter-processcommunication (IPC) protocols are used.

This enables the configuration of the D-CMTS shelf, and indeed theoverall network, to be rapidly reconfigured to meet the ever changingnetwork model generated by the invention. Often it will be convenient tostore this network configuration, as well as the properties of thevarious network devices, in a configuration database (630) andconfiguration database memory device (not shown).

FIG. 8 shows more details of the Cable Modem Remote Termination SystemCMRTS (604) portion of the D-CMRTS fiber node. At a higher or at leastalternate level of abstraction, the CMRTS portion of the D-CMRTS fibernode may typically comprise at least a first set of QAM-RF packetprocessors (700) with MAC and PHY units that select the desired opticalIP downstream data from the GigE formatted data, and convert thedownstream optical IP packet data to a plurality of radiofrequency (RF)QAM waveforms (channels) and output this data downstream (702) to thelocal CATV cable.

This CMRTS unit (604) may also optionally comprise a second set ofRF-upstream packet processors (704) that will read the upstream RFsignals (data) sent by cable modems connected to the local CATV cable(706). Note that these packet processors (704) may contain MAC and PHYunits that are capable of recognizing the upstream data. Thus if theupstream data is sent using an unusually wide upstream bandwidthaccording to scheme (390), the MAC and PHY units will recognize it. Theunits will then convert this upstream data to appropriate optical IPEthernet data packets, or other digital optical data communicationsprotocols suitable for communicating this cable modem data back upstreamto the improved D-CMTS (500) at the cable head.

The operation of both packet processors (700), (704) as well as otherdevices such as O-D/A-RF or RF-A/D-O converters (600), (601), QAMremodulators and demodulators (603), (605), CMRTS unit (604) and thelike may be remotely controlled by the virtual shelf manager (622) byway of suitable controllers (often microprocessors), and localapplications software (Apps) that intercept data from the optical fiber(222) and receive and send commands, often by way of a specializedcommunications protocol such as the previously discussed socketsprotocol.

At a deeper level that exposes more details of the PHY units in both theQAM-RF packet processor (700) and the optional RF-upstream packetprocessor (704), The CMRTS unit (604) will normally comprise MAC and PHYunits, and a data switch (710), at least one controller (often amicroprocessor and associated software, not shown), various QAMmodulators (712) to take the GigE data and convert, QAM modulate, andfrequency shift the data as needed to fit the limited CATV RF bandwidth.To do this, CMRTS unit may employ a controllable clock generator (714)to control the frequency and timing of the QAM channels, as well asvariable gain amplifier (VGA) units (716), (718) to help the PHYportions of the units manage the analog processes in converting signalsback and forth between the CMRTS unit (300) and the cable RF signals.

As before, the MAC and PHY units and the data switch (710) switches, andthe switches that control the QAM modulators (712) and analog to digital(A/D) units (720) may be remotely controlled by the virtual shelfmanager (622) by local (embedded) controllers (often microprocessors)and associated applications software by commands to and from the VirtualShelf software. As before, often these commands may be sent over thesame optical fiber pathways normally used to transmit other data, andagain may use socket based inter-process communication (IPC) protocols.

As before, for backward compatibility, the return process for processingupstream data can optionally implement the RF-A/D-O converters (601)and/or QAM demodulators (605) digitize and send the upstream signalsback with essentially no modification other than digitization, datapacket conversion, and optical conversion process.

Generally, the upstream data will be detected by whatever equipment isbest suited to interpret the invention's various upstream datamodulation methods—e.g. suitable equipment to intercept and decode thewider bandwidth upstream data and the like.

In this scheme, for simplicity, it is assumed that these methods will beimplemented by high speed DSP or software controlled receiver that canamplify the various signals, digitize them, and then decode according tothe appropriate algorithms, but of course other methods may also beused. Other hardware, such as ASICs, FPGA, DSP, and the like may also beused, as per U.S. patent application Ser. No. 13/555,170, the contentsof which are incorporated herein by reference.

In one embodiment, variable gain amplifier (VGA) units (718) willconvert the incoming upstream RF signal from the local neighborhood CATVcable into a signal which is then digitized by the A/D converter andclock generator, analyzed and repackaged by the MAC and PHY units (710)into a GigE or other optical fiber optimized signal, and then sentupstream along the optical fiber through various optical fibersplitter/combiner units (710). This process may be controlled bycommands from the Virtual Shelf software.

FIG. 9 shows more details of how the virtual shelf manager (622) and theconfiguration database (630) (previously shown in FIG. 7) may controlthe functionality of most or all of the plurality of D-CMRTS fiber nodes(300), improved D-CMTS (500) D-CMTS line cards (502), and optionallyother active nodes and switches in the HFC network system.

In this example, the virtual shelf manager software (622) is shownrunning as a module of a broader D-CMTS manager software package (800);however it also may be run as a standalone package. The D-CMTS managersoftware (800), which will often be run on one or more computerprocessors which may be located at the cable head or other convenientlocation, will often be based on network configuration managementsoftware (802). Such network configuration software (802) (also calledthe Operational Support Systems (OSS) software) may be, for example,software based upon the ConfD network management software produced byTail-f Systems Corporation, Stockholm Sweden (International location)and Round Hill Va. (US location).

In this embodiment, use of software such as ConfD is useful because thistype of network management software also provides a number of convenientand commonly used interfaces to allow users to interact with the networkand control then network configuration. These interfaces may includeNETCONF management agents, SNMP agents, Command Line Interfaces (CLI),Internet (Web) interfaces, and other agents/interfaces as desired.

The virtual CMTS shelf software that may be used to control the statusof the various D-CMTS line cards (500) and D-CMRTS fiber nodes (300)will often interact with a network configuration database (630) rununder the control of this network configuration software (802). Thevirtual D-CMTS shelf software will in turn send commands out to most orall of the various remote D-CMRTS fiber nodes, as well as control theoperation of the D-CMTS (500) at the cable head and other devices asdesired. As previously discussed, one preferred way for this control tobe achieved is by way of socket based inter-process communication (IPC)protocols and packets (804), which may be sent over the same opticalfiber lines used to send the other data. In this situation, for example,controllers running various types of application software (Apps) in theplurality of remote packet processors (700), (704) in the remote D-CMRTSfiber nodes (300) can listen for appropriate commands from the virtualshelf manager (622), and adjust the operation of the D-CMRTS packet(700), (704) processors accordingly. These D-CMRTS fiber nodes can alsotransmit their status back to the virtual shelf manager using the sameprotocols.

The device configuration database (630) of the virtual shelf managersystem will often have multiple data fields, including fields thatcontain the identification code and/or addresses of the various D-CMRTSunits in the network (D-CMRTS identifier fields). The database will alsousually have information on the status of the various cable modemsconnected to the various D-CMRTS units, including the cable modemidentification data (cable modem identification data fields) and theprivileges of the various users that are associated these various cablemodems. For example, one user may have privileges to access a broadarray of services high bandwidth upload and download data, while anotheruser may have limited access to a different set of services and morelimited upload and download data privileges. Other functions that may beimplemented include event logging, Authentication, Authorization andAccounting (AAA) support, an extended version of a DOCSIS ManagementInformation BASE (MIBs) functions, etc.

Other fields that normally will be in the database will includeinformation as to user identification fields (user privilege fields),available extended DOCSIS channels, available IP addresses, instructionsfor how to remotely configure the various D-CMRTS software controllableswitches, and instructions for how to remotely configure the variousD-CMRTS software controllable RF packet processors.

The virtual shelf manager and configuration database, as well as othercomponents of the system, will usually be run on a computer system withat least one microprocessor, as well as standard hardware and software,such as MAC and PHY units, that will enable the virtual shelf manager tosend and receive data packets (often through the IPC protocol) to thevarious remote D-CMRTS units on the network.

The OSS software (802) can inform the virtual shelf manager softwareabout the privileges, certificates, and encryption keys assigned to thevarious users. The OSS can also set policies or allocation limitsregarding the frequency and bandwidth that will be assigned to thevarious channels. The OSS can also respond to queries from the virtualshelf manager when new modems are detected. The OSS can further takestatistical data collected by the virtual shelf manager, such as packetstransmitted and received, volume of data, and use this information forbilling and network management purposes.

Further information on OSS functions, and more examples of functionsthat may be implemented in the OSS software for the invention, may befound in Misra, “OSS for Telecom Networks: An Introduction to NetworkManagement”, Springer (2004).

For example how this system would operate, consider the case where a newcable modem is first connected to the system. The cable modem may sendan upstream signal (226) to the D-CMRTS (604). The RF-up packetprocessor (704) in the DCMRTS (604) will in turn collect the informationrelating to the cable modem identification number, and other relevantparameters, repackage the data in a digital format, and send it backupstream to the virtual shelf manager system on the fiber GigE link(302). The virtual shelf manager system (622) will look up the cablemodem identification data in the device configuration database (630),and determine the privileges of the user associated with said cablemodem identification data, and depending upon the value of the userprivilege field, available extended DOCSIS channels, and available IPaddresses, send data packets to the D-CMRTS (700) unit, often by way ofthe IPC protocol (804) that controls that particular cable modem. Thevirtual shelf manager may also control the function of any householdgateway devices.

These data packets will interact with applications (e.g. App 1, App n)and configure the software controllable switch(s) on the D-CMRTS unit(700), to configure the software controllable switches on the QAM-RFpacket processor (700) and the cable modem available IP addresses orTDD-FDD gateway addresses so as transmit downstream data to the cablemodem on a first available DOCSIS channel. The data packets will alsoconfigure the software controllable RF packet processor (704) to receiveupstream data from the cable modem on a second available DOCSIS upstreamchannel and IP address and retransmit the upstream data as a thirdupstream digital optical fiber signal (302).

Often the virtual shelf manager (622) will handle IP addresses for thecable modems and optional gateway devices through the proxy Dynamic HostConfiguration Protocol (DHCP) service, or other method.

Alternative types of residential gateways capable of allowing householdCATV equipment that is designed for the standard DOCSIS CATV protocolsthat call for the 5-42 MHz range of upstream frequencies to work withCATV cables an extended range of upstream frequencies are also possible.This gateway equipment will be designed to “fool” the household CATVequipment into thinking that it is connected to a standard CATV cablethat is capable of carrying standard 5-42 MHz upstream data, but thatthis standard CATV cable is relatively uncongested—that is that acomparatively large portion of the 5-42 MHz spectrum is free for use. Infact, the gateway equipment may then either shift the frequency of thehousehold 5-42 MHz upstream data (e.g. QAM channels) to an alternatefrequency (e.g. convert a 20 MHz upstream QAM channel to, for example, a100 MHz QAM channel) for transmission over the CATV cable, oralternatively convert the upstream QAM channel(s) into spread spectrumsignals. In either event, the converted upstream signals will then besent upstream on the CATV cable to the D-CMRTS optical fiber node, orother fiber node as appropriate. This data may then be converted tooptical fiber data and sent on to the cable head as appropriate.

Adaptive cancellation methods, useful for such adjustableupstream/downstream frequency ranges were taught in copendingapplication Ser. No. 13/400,415 “METHODS OF ADAPTIVE CANCELLING ANDSECONDARY COMMUNICATIONS CHANNELS FOR EXTENDED CAPABILITY HFC CABLESYSTEMS”, the contents of which are incorporated herein by reference.

FIG. 10 shows an alternate type of residential gateway (1100) that canconvert between a CATV cable system with an extended frequency allocatedfor upstream data (e.g. 5-547 MHz or alternative upstream range offrequencies), and residential equipment designed for the standard 5-42MHz range of upstream frequencies.

Here CATV cable 226 is carrying extended range frequency upstream data(390), which may have far more upstream MHz bandwidth than the standardlimited CATV 5-42 MHz upstream bandwidth. However the problem is thatwithin the household, the CATV equipment—e.g. set top boxes, cablemodems, may be legacy CATV equipment that only is capable of sendingupstream data on the standard 5-42 MHz bandwidth. In this example, thegateway (1100) serving the house may be an extended FDD upstream gatewaythat contains the equipment necessary to frequency shift the householdCATV equipment upstream signals to alternate frequencies forretransmission on the CATV cable (226). Thus, for example, the upstreamdata capability of a neighborhood could be extended about 10× byreallocating and transmitting the normal 5-42 MHz upstream data in abroader 5-547 MHz range, and tricking every household into thinking thatit had free access to a 5-42 MHz upstream range of frequencies that wasonly 1/10 as congested as it was before.

As previously discussed, alternate types of gateways are also possible.Such alternative methods were discussed in copending application Ser.No. 13/035,993 “METHOD OF CATV CABLE SAME-FREQUENCY TIME DIVISION DUPLEXDATA TRANSMISSION”, the contents of which are incorporated herein byreference.

Other alternative embodiments of the invention are also possible. Inthese alternative embodiments, the CMRTS or D-CMRTS units can havemultiple outputs, such as multiple CATV cable outputs, or even a mix ofCATV or Coax cable outputs and, other output types such as data outputs(e.g. GigE or other data output), telephony outputs, and the like.

Other applications: The present invention may also be used foralternative HFC configurations, such as copending application Ser. No.13/346,709 “HFC CABLE SYSTEM WITH WIDEBAND COMMUNICATIONS PATHWAY ANDCOAX DOMAIN NODES”, and Ser. No. 12/907,970 “HFC CABLE SYSTEM WITHSHADOW FIBER AND COAX FIBER TERMINALS”, the contents of which areincorporated herein by reference.

The invention claimed is:
 1. A digital optical fiber node system for aHybrid Fiber Cable (HFC) network, the system comprising: a cable headend (CHE) for transmitting internet protocol (IP) data packetscomprising Quadrature Amplitude Modulation (QAM) symbols over an opticalfiber; a digital optical fiber node for (i) receiving the IP datapackets, (ii) generating downstream radio frequency (RF) signals thatare modulated according to the QAM symbols carried by the IP datapackets, and (iii) transmitting the generated downstream RF signals overa set of cable television (CATV) cables to a plurality of cable modems.2. The system of claim 1 further comprising a plurality of digitaloptical fiber nodes that includes the digital optical fiber node,wherein each digital optical fiber node comprises a different addressand received IP data packets are associated with the different address.3. The system of claim 2 further comprising a multiple port switch for:identifying each of the different addresses of the plurality of digitaloptical fiber nodes; and directing IP data packets to a specific digitaloptical fiber node corresponding to an address associated with the IPdata packets.
 4. The system of claim 1, wherein the QAM symbols are afirst set of QAM symbols, wherein the system further comprises adownstream converter device for: accepting a plurality of RF signalsfrom the CHE; digitizing a first set of RF signals from the plurality ofRF signals into a set of digital samples for transmission over theoptical fiber; and demodulating a second set of RF signals from theplurality of RF signals into a set of data packets comprising a secondset of QAM symbols for transmission over the optical fiber.
 5. Thesystem of claim 1, wherein the generated downstream RF signals comprisea first set of downstream RF QAM signals, wherein the digital opticalfiber node is further for: receiving the set of digital samples and theset of data packets; reconstituting the received set of digital samplesinto a set of downstream digitally reconstructed RF signals; convertingthe second set of QAM symbols into a second set of downstream RF QAMsignals; and transmitting the set of downstream digitally reconstructedRF signals and the second set of downstream RF QAM signals over the setof CATV cables.
 6. The system of claim 5, wherein the set of downstreamdigitally reconstructed RF signals comprise at least one of analogNational Television System Committee (NTSC) television channels,frequency modulation (FM) audio channels, and Quadraphase-shift keying(QPSK) channels, wherein the second set of RF QAM downstream signalscomprise at least one of standard definition television channels andhigh definition digital television channels, wherein the first set ofdownstream RF QAM signals comprise at least one of data over cableservice interface specifications (DOCSIS) channels, edge QAM channels,video on demand channels, and IP data streams.
 7. The system of claim 5,wherein the transmitting the set of downstream digitally reconstructedRF signals and the second set of RF QAM downstream signals comprisescombining the first set of downstream RF QAM signals, the second set ofdownstream RF QAM signals, and the set of downstream digitallyreconstituted RF signals for transmission over the set of CATV cables.8. The system of claim 1, wherein the digital optical fiber node isfurther for: accepting upstream RF signals transmitted over the set ofCATV cables from the set of cable modems; and digitizing the upstream RFsignals in order to produce digitally encoded upstream RF channel datafor transmission over the optical fiber to the CHE.
 9. The system ofclaim 8, wherein the digital optical fiber node is further for enablingvariable frequency cutoff between RF frequencies of upstream RF signalsdesignated for transmission over the optical fiber and RF frequencies ofgenerated downstream RF signals designated for transmission over the setof CATV cables.
 10. The system of claim 8, wherein the digital opticalfiber node is further for decomposing the upstream RF signals into aplurality of subbands, wherein the upstream RF signals are digitized byusing at least some of the plurality of subbands.
 11. The system ofclaim 1, wherein the IP data packets further comprise digitized RFsamples, wherein the generated downstream RF signals further comprise RFwaveforms that are reconstituted from the RF samples.
 12. A method oftransmitting data over a Hybrid Fiber Cable (HFC) network, the methodcomprising: receiving, at a digital optical fiber node, internetprotocol (IP) data packets from a cable head end (CHE) over an opticalfiber, the IP data packets comprising Quadrature Amplitude Modulation(QAM) symbols; and generating downstream radio frequency (RF) signalsthat are modulated according to the QAM symbols carried by the IP datapackets; and transmitting the generated downstream RF signals over a setof cable television (CATV) cables to a plurality of cable modems. 13.The method of claim 12, wherein the digital optical fiber node is one ofa plurality of digital optical fiber nodes, each digital optical fibernode comprises a different address, wherein the received IP data packetsare associated with a specific address that corresponds to an addressassociated with the digital optical fiber node.
 14. The method of claim12 further comprising: accepting upstream RF signals transmitted overthe set of CATV cables from the set of cable modems; and digitizing theupstream RF signals in order to produce digitally encoded upstream RFchannel data for transmission over the optical fiber to the CHE.
 15. Themethod of claim 14 further comprising enabling variable frequency cutoffbetween RF frequencies of upstream RF signals designated fortransmission over the optical fibers and RF frequencies of generateddownstream RF signals designated for transmission over the set of CATVcables.
 16. The method of claim 14 further comprising decomposing theupstream RF signals into a plurality of subbands, wherein the upstreamRF signals are digitized by using at least some of the plurality ofsubbands.
 17. The method of claim 12, wherein the QAM symbols are afirst set of QAM symbols and the generated downstream RF signalscomprise a first set of downstream RF QAM signals, wherein the methodfurther comprises: receiving a set of digital samples and a set of datapackets comprising a second set of QAM symbols; reconstituting thereceived set of digital samples into a set of downstream digitallyreconstructed RF signals; converting the second set of QAM symbols intoa second set of downstream RF QAM signals; and transmitting the set ofdownstream digitally reconstructed RF signals and the second set ofdownstream RF QAM signals over the set of CATV cables.
 18. The method ofclaim 17, wherein transmitting the set of downstream digitallyreconstructed RF signals and the second set of RF QAM downstream signalscomprises combining the first set of downstream RF QAM signals, thesecond set of downstream RF QAM signals, and the set of downstreamdigitally reconstituted RF signals for transmission over the set of CATVcables.
 19. The method of claim 17, wherein the set of downstreamdigitally reconstructed RF signals comprise at least one of analogNational Television System Committee (NTSC) television channels,frequency modulation (FM) audio channels, and Quadraphase-shift keying(QPSK) channels, wherein the second set of RF QAM downstream signalscomprise at least one of standard definition television channels andhigh definition digital television channels, wherein the first set ofdownstream RF QAM signals comprise at least one of data over cableservice interface specifications (DOCSIS) channels, edge QAM channels,video on demand channels, and IP data streams.
 20. The method of claim12, wherein the IP data packets further comprise digitized RF samples,wherein the generated downstream RF signals further comprise RFwaveforms that are reconstituted from the RF samples.